Charged-particle production was studied in proton-proton collisions collected at the LHC with the ALICE detector at centre-of-mass energies 0.9 TeV and 2.36 TeV in the pseudorapidity range |$\eta$| < 1.4. In the central region (|$\eta$| < 0.5), at 0.9 TeV, we measure charged-particle pseudorapidity density dNch/deta = 3.02 $\pm$ 0.01 (stat.) $^{+0.08}_{-0.05}$ (syst.) for inelastic interactions, and dNch/deta = 3.58 $\pm$ 0.01 (stat.) $^{+0.12}_{-0.12}$ (syst.) for non-single-diffractive interactions. At 2.36 TeV, we find dNch/deta = 3.77 $\pm$ 0.01 (stat.) $^{+0.25}_{-0.12}$ (syst.) for inelastic, and dNch/deta = 4.43 $\pm$ 0.01 (stat.) $^{+0.17}_{-0.12}$ (syst.) for non-single-diffractive collisions. The relative increase in charged-particle multiplicity from the lower to higher energy is 24.7% $\pm$ 0.5% (stat.) $^{+5.7}_{-2.8}$% (syst.) for inelastic and 23.7% $\pm$ 0.5% (stat.) $^{+4.6}_{-1.1}$% (syst.) for non-single-diffractive interactions. This increase is consistent with that reported by the CMS collaboration for non-single-diffractive events and larger than that found by a number of commonly used models. The multiplicity distribution was measured in different pseudorapidity intervals and studied in terms of KNO variables at both energies. The results are compared to proton-antiproton data and to model predictions.
Measured pseudorapidity dependence of DN/DETARAP for INEL collisions at a centre-of-mass energy of 900 GeV.
Measured pseudorapidity dependence of DN/DETARAP for NSD collisions at a centre-of-mass energy of 900 GeV.
Measured pseudorapidity dependence of DN/DETARAP for INEL collisions at a centre-of-mass energy of 2360 GeV.
The PHENIX experiment has studied nuclear effects in $p$$+$Al and $p$$+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV on charged hadron production at forward rapidity ($1.4<\eta<2.4$, $p$-going direction) and backward rapidity ($-2.2<\eta<-1.2$, $A$-going direction). Such effects are quantified by measuring nuclear modification factors as a function of transverse momentum and pseudorapidity in various collision multiplicity selections. In central $p$$+$Al and $p$$+$Au collisions, a suppression (enhancement) is observed at forward (backward) rapidity compared to the binary scaled yields in $p$+$p$ collisions. The magnitude of enhancement at backward rapidity is larger in $p$$+$Au collisions than in $p$$+$Al collisions, which have a smaller number of participating nucleons. However, the results at forward rapidity show a similar suppression within uncertainties. The results in the integrated centrality are compared with calculations using nuclear parton distribution functions, which show a reasonable agreement at the forward rapidity but fail to describe the backward rapidity enhancement.
RpA of charged hadrons as a function of pT at forward and backward rapidity in p+Al 0%-100% centrality.
RpA of charged hadrons as a function of pT at forward and backward rapidity in p+Au 0%-100% centrality.
RpA of charged hadrons as a function of eta at forward and backward rapidity in p+Al and p+Au 0%-100% centrality.
Inclusive production of $\mathrm{D^{*\pm}}$ mesons in two-photon collisions was measured by the L3 experiment at LEP. The data were collected at a centre-of-mass energy $\sqrt{s} = 189$ GeV with an integrated luminosity of $176.4 \mathrm{pb^{-1}}$. Differential cross sections of the process $\mathrm{e^+e^- \to D^{*\pm} X}$ are determined as functions of the transverse momentum and pseudorapidity of the $\mathrm{D^{*\pm}}$ mesons in the kinematic region 1 GeV $< p_{T}^{\mathrm{D^*}} < 5 $ GeV and $\mathrm{|\eta^{D^*}|} < 1.4$. The cross section integrated over this phase space domain is measured to be $132 \pm 22(stat.) \pm 26(syst.)$ pb. The differential cross sections are compared with next-to-leading order perturbative QCD calculations.
The measured cross sections, as a function of PT over the bin ranges and the differential cross sections after bin-centre corrections.
The measured cross sections, as a function of pseudorapidity over the bin ranges and the differential cross sections after bin-centre corrections.
Integrated cross section in the visible kinematic region.
Measurements of charged particle distributions, sensitive to the underlying event, have been performed with the ATLAS detector at the LHC. The measurements are based on data collected using a minimum-bias trigger to select proton-proton collisions at center-of-mass energies of 900 GeV and 7 TeV. The 'underlying event' is defined as those aspects of a hadronic interaction attributed not to the hard scattering process, but rather to the accompanying interactions of the rest of the proton. Three regions are defined in azimuthal angle with respect to the highest-pt charged particle in the event, such that the region transverse to the dominant momentum-flow is most sensitive to the underlying event. In each of these regions, distributions of the charged particle multiplicity, pt density, and average pt are measured. The data show a higher underlying event activity than that predicted by Monte Carlo models tuned to pre-LHC data.
Particle Number Density versus Lead Particle PT at centre-of-mass energy 900 GeV.
Particle Number Density versus Lead Particle PT at centre-of-mass energy 7000 GeV.
Particle PT Density versus Lead Particle PT at centre-of-mass energy 900 GeV.
The production of Kshort and Lambda hadrons is studied in inelastic pp collisions at sqrt(s) = 0.9 and 7 TeV collected with the ATLAS detector at the LHC using a minimum-bias trigger. The observed distributions of transverse momentum, rapidity, and multiplicity are corrected to hadron level in a model-independent way within well defined phase-space regions. The distribution of the production ratio of Lambdabar to Lambda baryons is also measured. The results are compared with various Monte Carlo simulation models. Although most of these models agree with data to within 15% in the Kshort distributions, substantial disagreements with data are found in the Lambda distributions of transverse momentum.
The corrected transverse momentum distribution of KS mesons at 7000 GeV.
The corrected rapidity distribution of KS mesons at 7000 GeV.
The corrected multiplicity distribution of KS mesons at 7000 GeV.
We present a measurement of two-particle angular correlations in proton-proton collisions at sqrt(s) = 900 GeV and 7 TeV. The collision events were collected during 2009 and 2010 with the ATLAS detector at the Large Hadron Collider using a single-arm minimum bias trigger. Correlations are measured for charged particles produced in the kinematic range of transverse momentum pT > 100 MeV and pseudorapidity |eta| < 2.5. A complex structure in pseudorapidity and azimuth is observed at both collision energies. Results are compared to Pythia 8 and Herwig++ as well as to the AMBT2B, DW and Perugia 2011 tunes of Pythia 6. The data are not satisfactorily described by any of these models.
Corrected two particle RCORR distribution as a function of Delta(ETARAP) obtained by integrating the foreground and background distributions over Delta(PHI) between 0 and PI.
Corrected two particle RCORR distribution as a function of Delta(ETARAP) obtained by integrating the foreground and background distributions over Delta(PHI) between 0 and PI/2.
Corrected two particle RCORR distribution as a function of Delta(ETARAP) obtained by integrating the foreground and background distributions over Delta(PHI) between PI/2 and PI.
Using inelastic proton-proton interactions at sqrt(s) = 900 GeV and 7 TeV, recorded by the ATLAS detector at the LHC, measurements have been made of the correlations between forward and backward charged-particle multiplicities and, for the first time, between forward and backward charged-particle summed transverse momentum. In addition, jet-like structure in the events is studied by means of azimuthal distributions of charged particles relative to the charged particle with highest transverse momentum in a selected kinematic region of the event. The results are compared with predictions from tunes of the PYTHIA and HERWIG++ Monte Carlo generators, which in most cases are found to provide a reasonable description of the data.
$\sqrt{s} = 900$ GeV, $p_T > 500 $ MeV, $|\eta|<1$.
$\sqrt{s} = 7$ TeV, $p_T > 500 $ MeV, $|\eta|<1$.
$\sqrt{s} = 900$ GeV, $p_T > 500 $ MeV, $|\eta|<2$.
We present first measurements of charged and neutral particle-flow correlations in pp collisions using the ATLAS calorimeters. Data were collected in 2009 and 2010 at centre-of-mass energies of 900 GeV and 7 TeV. Events were selected using a minimum-bias trigger which required a charged particle in scintillation counters on either side of the interaction point. Particle flows, sensitive to the underlying event, are measured using clusters of energy in the ATLAS calorimeters, taking advantage of their fine granularity. No Monte Carlo generator used in this analysis can accurately describe the measurements. The results are independent of those based on charged particles measured by the ATLAS tracking systems and can be used to constrain the parameters of Monte Carlo generators.
900 GeV Particle density vs. Delta(phi) with leading particle pT > 1 GeV.
900 GeV Particle density vs. Delta(phi) with leading particle pT > 2 GeV.
900 GeV Particle density vs. Delta(phi) with leading particle pT > 3 GeV.
The paper presents studies of Bose-Einstein Correlations (BEC) for pairs of like-sign charged particles measured in the kinematic range $p_{\rm T}>$ 100 MeV and $|\eta|<$ 2.5 in proton--proton collisions at centre-of-mass energies of 0.9 and 7 TeV with the ATLAS detector at the CERN Large Hadron Collider. The integrated luminosities are approximately 7 $\mu$b$^{-1}$, 190 $\mu$b$^{-1}$ and 12.4 nb$^{-1}$ for 0.9 TeV, 7 TeV minimum-bias and 7 TeV high-multiplicity data samples, respectively. The multiplicity dependence of the BEC parameters characterizing the correlation strength and the correlation source size are investigated for charged-particle multiplicities of up to 240. A saturation effect in the multiplicity dependence of the correlation source size is observed using the high-multiplicity 7 TeV data sample. The dependence of the BEC parameters on the average transverse momentum of the particle pair is also investigated.
Systematic uncertainties on $\lambda$ and $R$ for the exponential fit of the two-particle double-ratio correlation function $R_{2}(Q)$ in the full kinematic region at $\sqrt{s} = 0.9$ and $7\ TeV$ for minimum-bias and high-multiplicity (HM) events, $n_{ch} \ge 2$ and $n_{ch} \ge 150$, respectively.
Results of fitting the multiplicity, $n_{ch}$, dependence of the BEC parameters $R$ and $\lambda$ with different functional forms for $\sqrt{s} = 0.9$ and $7\ TeV$. The $n_{ch}$ fit of $R(n_{ch})$ is applied to $7\ TeV$ minimum-bias events at $n_{ch} \le 55$ and to $0.9\ TeV$ minimum-bias events. The constant fit of $R(n_{ch} )$ is applied to $7\ TeV$ minimum-bias events for $n_{ch} > 55$ and to $7\ TeV$ high-multiplicity events. The exponential fit of $\lambda(n_{ch})$ is applied to $7\ TeV$ minimum-bias and high-multiplicity events.The error represent the quadratic sum of the statistical and systematic uncertainties.
Results of fitting the transverse momentum of the pair, $k_{T}$, dependence of the BEC parameters $R$ and $\lambda$ with the exponential fitting function for $\sqrt{s} = 0.9$ and $7\ TeV$. The error represent the quadratic sum of the statistical and systematic uncertainties.
This paper presents a measurement of the ordering of charged hadrons in the azimuthal angle relative to the beam axis in high-energy proton-proton collisions at the Large Hadron Collider (LHC). A spectral analysis of correlations between longitudinal and transverse components of the momentum of the charged hadrons, driven by the search for phenomena related to the structure of the QCD field, is performed. Data were recorded with the ATLAS detector at centre-of-mass energies of sqrt(s) = 900 GeV and sqrt(s) = 7 TeV. The correlations measured in a phase space region dominated by low-pT particles are not well described by conventional models of hadron production. The measured spectra show features consistent with the fragmentation of a QCD string represented by a helix-like ordered gluon chain.
The corrected data for the power spectra S_E for the three different data samples at a centre-of-mass energy of 7 TeV.
The corrected data for the power spectra S_ETA for the three different data samples at a centre-of-mass energy of 7 TeV.
The corrected data for the power spectra S_E for the three different data samples at a centre-of-mass energy of 900 GeV.
A measurement of the direct production of photons with high transverse momentum from\(\bar pp\) collisions at\(\sqrt s= 630\) GeV is presented. The structure of events containing a high transverse momentum photon is studied. The results support predictions from QCD theory.
The last data point is an average over the interval 60-100 GeV in which 5 events are found.
No description provided.
No description provided.
We report on the nuclear dependence of transverse single-spin asymmetries (TSSAs) in the production of positively-charged hadrons in polarized $p^{\uparrow}+p$, $p^{\uparrow}+$Al and $p^{\uparrow}+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV. The measurements have been performed at forward rapidity ($1.4<\eta<2.4$) over the range of $1.8<p_{T}<7.0$ GeV$/c$ and $0.1<x_{F}<0.2$. We observed a positive asymmetry $A_{N}$ for positively-charged hadrons in \polpp collisions, and a significantly reduced asymmetry in $p^{\uparrow}$+$A$ collisions. These results reveal a nuclear dependence of charged hadron $A_N$ in a regime where perturbative techniques are relevant. These results provide new opportunities to use \polpA collisions as a tool to investigate the rich phenomena behind TSSAs in hadronic collisions and to use TSSA as a new handle in studying small-system collisions.
$A_N$ as a function of $A^{1/3}$ for positively-charged hadrons at 1.4 < $\eta$ < 2.4, 0.1 < $x_F$ < 0.2, and 1.8 < $p_T$ < 7.0 GeV/$c$ in $p^{\uparrow}$+$p$, $p^{\uparrow}$+Al, and $p^{\uparrow}$+Au collisions.
$A_N$ as a function of $N^{Avg.}_{coll}$ for positively-charged hadrons at 1.4 < $\eta$ < 2.4, 0.1 < $x_F$ < 0.2, and 1.8 < $p_T$ < 7.0 GeV/$c$ in $p^{\uparrow}$+$p$, $p^{\uparrow}$+Al, and $p^{\uparrow}$+Au collisions.
The cross section and transverse single-spin asymmetries of $\mu^{-}$ and $\mu^{+}$ from open heavy-flavor decays in polarized $p$+$p$ collisions at $\sqrt{s}=200$ GeV were measured by the PHENIX experiment during 2012 at the Relativistic Heavy Ion Collider. Because heavy-flavor production is dominated by gluon-gluon interactions at $\sqrt{s}=200$ GeV, these measurements offer a unique opportunity to obtain information on the trigluon correlation functions. The measurements are performed at forward and backward rapidity ($1.4<|y|<2.0$) over the transverse momentum range of $1.25<p_T<7$ GeV/$c$ for the cross section and $1.25<p_T<5$ GeV/$c$ for the asymmetry measurements. The obtained cross section is compared to a fixed-order-plus-next-to-leading-log perturbative-quantum-chromodynamics calculation. The asymmetry results are consistent with zero within uncertainties, and a model calculation based on twist-3 three-gluon correlations agrees with the data.
$A_N$ of negatively-charged muons from open heavy-flavor decays as a function of $p_T$ in the backward ($x_F$ < 0) and forward ($x_F$ > 0) regions.
$A_N$ of positively-charged muons from open heavy-flavor decays as a function of $p_T$ in the backward ($x_F$ < 0) and forward ($x_F$ > 0) regions.
$A_N$ of negatively-charged and positively-charged muons from open heavy-flavor decays as a function of $x_F$, where $x_F$ > 0 is along the direction of the polarized proton.
Inclusive D^{*+-} production in two-photon collisions is studied with the L3 detector at LEP, using 683 pb^{-1} of data collected at centre-of-mass energies from 183 to 208 GeV. Differential cross sections are determined as functions of the transverse momentum and pseudorapidity of the D^{*+-} mesons in the kinematic region 1 GeV < P_T < 12 GeV and |eta| < 1.4. The cross sections sigma(e^+e^- -> e^+e^-D^{*+-}X) in this kinematical region is measured and the sigma(e^+e^- -> e^+e^- cc{bar}X) cross section is derived. The measurements are compared with next-to-leading order perturbative QCD calculations.
Visible D*+- production cross section in the given phase space range. Data are given for each D* decay channel, and the average.
Total cross section for open charm production. Data are given for each D* decay channel, and the combined average. The second systematic (DSYS) error is the uncertainty on the extrapolation from the visible to the full phase space region.
The measured D*+- production cross section in the region ABS(ETARAP) < 1.4.The DSIG/DPT points refer to the centre of the bin and the SIG points are the integrated over the bin.
Inclusive-jet and dijet differential cross sections have been measured in neutral current deep inelastic ep scattering for exchanged boson virtualities Q2 > 125 GeV2 with the ZEUS detector at HERA using an integrated luminosity of 82 pb-1. Jets were identified in the Breit frame using the kt cluster algorithm. Jet cross sections are presented as functions of several kinematic and jet variables. The results are also presented in different regions of Q2. Next-to-leading-order QCD calculations describe the measurements well. Regions of phase space where the theoretical uncertainties are small have been identified. Measurements in these regions have the potential to constrain the gluon density in the proton when used as inputs to global fits of the proton parton distribution functions.
Dijet cross section as a function of Q**2 in the Breit frame.
Dijet cross section as a function of Bjorken X in the Breit frame.
Dijet cross section as a function of the mean ET of the jets in the Breit frame.
Inclusive jet differential cross sections have been measured in neutral current deep inelastic e+p scattering for boson virtualities Q**2>125 GeV**2. The data were taken using the ZEUS detector at HERA and correspond to an integrated luminosity of 38.6 pb-1. Jets were identified in the Breit frame using the longitudinally invariant K_T cluster algorithm. Measurements of differential inclusive jet cross sections are presented as functions of jet transverse energy (E_T,jet), jet pseudorapidity and Q**2, for jets with E_T,jet>8 GeV. Next-to-leading-order QCD calculations agree well with the measurements both at high Q**2 and high E_T,jet. The value of alpha_s(M_Z), determined from an analysis of dsigma/dQ**2 for Q**2>500 GeV**2, is alpha_s(M_Z) = 0.1212 +/- 0.0017 (stat.) +0.0023 / -0.0031 (syst.) +0.0028 / -0.0027 (th.).
Inclusive jet cross section DSIG/DQ**2 for jets of hadrons in the Breit frame.
Inclusive jet cross section DSIG/DET for jets of hadrons in the Breit frame.
Inclusive jet cross section DSIG/DETARAP for jets of hadrons in the Breit frame.
Single- and double-differential inclusive dijet cross sections in neutral current deep inelastic ep scattering have been measured with the ZEUS detector using an integrated luminosity of 374 pb^-1. The measurement was performed at large values of the photon virtuality, Q^2, between 125 and 20000 GeV^2. The jets were reconstructed with the k_T cluster algorithm in the Breit reference frame and selected by requiring their transverse energies in the Breit frame, E_T,B^jet, to be larger than 8 GeV. In addition, the invariant mass of the dijet system, M_jj, was required to be greater than 20 GeV. The cross sections are described by the predictions of next-to-leading-order QCD.
The measured differential cross-sections $d\sigma/dQ^2$ for inclusive dijet production. The statistical, uncorrelated systematic and jet-energy-scale (ES) uncertainties are shown separately. The multiplicative corrections, ${C_{\rm{QED}}}$, which have been applied to the data and the corrections for hadronisation and ${Z^{0}}$ effects to be applied to the parton-level NLO QCD calculations, ${C_{\rm{hadr}}\cdot C_{\rm{Z^{0}}}}$, are shown in the last two columns.
Inclusive dijet cross-sections ${d\sigma/dx_{\rm{Bj}}}$. Other details as in the caption to Table 1.
Inclusive dijet cross-sections ${d\sigma/d\overline{E^{jet}_{T,B}}}$. Other details as in the caption to Table 1.
Inclusive jet production is studied in neutral current deep-inelastic positron-proton scattering at large four momentum transfer squared Q^2>150 GeV^2 with the H1 detector at HERA. Single and double differential inclusive jet cross sections are measured as a function of Q^2 and of the transverse energy E_T of the jets in the Breit frame. The measurements are found to be well described by calculations at next-to-leading order in perturbative QCD. The running of the strong coupling is demonstrated and the value of alpha_s(M_Z) is determined. The ratio of the inclusive jet cross section to the inclusive neutral current cross section is also measured and used to extract a precise value for alpha_s(M_Z)=0.1193+/-0.0014(exp.)^{+0.0047}_{-0.0030}(th.)+/-0.0016(pdf).
Double differential cross section as a function of ET integrated over the ET bin range and the Q**2 range 150 to 200 GeV**2.
Double differential cross section as a function of ET integrated over the ET bin range and the Q**2 range 200 to 270 GeV**2.
Double differential cross section as a function of ET integrated over the ET bin range and the Q**2 range 270 to 400 GeV**2.
The cross section of W-boson pair-production is measured with the L3 detector at LEP. In a data sample corresponding to a total luminosity of 629.4/pb, collected at centre-of-mass energies ranging from 189 to 209 GeV, 9834 four-fermion events with W bosons decaying into hadrons or leptons are selected. The total cross section is measured with a precision of 1.4 % and agrees with the Standard Model expectation. Assuming charged-lepton universality, the branching fraction for hadronic W-boson decays is measured to be: Br(W-->hadrons) = 67.50 +- 0.42 (stat.) +- 0.30(syst.) %, in agreement with the Standard Model. Differential cross sections as a function of the W- production angle are also measured for the semi-leptonic channels qqev and qqmv.
Measured cross section for the process E+ E- --> LEPTON NU LEPTON NU.
Measured cross section for the process E+ E- --> QUARK QUARKBAR ELECTRON NEUTRINO.
Measured cross section for the process E+ E- --> QUARK QUARKBAR MUON NEUTRINO.
The production of jets is studied in deep-inelastic e+p scattering at low negative four momentum transfer squared 5<Q^2<100 GeV^2 and at inelasticity 0.2<y<0.7 using data recorded by the H1 detector at HERA in the years 1999 and 2000, corresponding to an integrated luminosity of 43.5 pb^-1. Inclusive jet, 2-jet and 3-jet cross sections as well as the ratio of 3-jet to 2-jet cross sections are measured as a function of Q^2 and jet transverse momentum. The 2-jet cross section is also measured as a function of the proton momentum fraction xi. The measurements are well described by perturbative quantum chromodynamics at next-to-leading order corrected for hadronisation effects and are subsequently used to extract the strong coupling alpha_s.
Inclusive Jet Cross Section ${\rm\frac{d\sigma_{jet}}{dQ^2}}$.
2-Jet Cross Section ${\rm\frac{d\sigma_{2-jet}}{dQ^2}}$.
3-Jet Cross Section ${\rm\frac{d\sigma_{3-jet}}{dQ^2}}$.
The production of jets is studied in deep-inelastic ep scattering at large negative four momentum transfer squared 150<Q^2<15000 GeV^2 using HERA data taken in 1999-2007, corresponding to an integrated luminosity of 395 pb^-1. Inclusive jet, 2-jet and 3-jet cross sections, normalised to the neutral current deep-inelastic scattering cross sections, are measured as functions of Q^2, jet transverse momentum and proton momentum fraction. The measurements are well described by perturbative QCD calculations at next-to-leading order corrected for hadronisation effects. The strong coupling as determined from these measurements is alpha_s(M_Z) = 0.1168 +/-0.0007 (exp.) +0.0046/-0.0030 (th.) +/-0.0016(pdf).
Normalised inclusive jet cross section in bins of $Q^{2}$.
Normalised 2-jet cross section in bins of $Q^{2}$.
Normalised 3-jet cross section in bins of $Q^{2}$.
We present measurements of azimuthal correlations of charged hadron pairs in $\sqrt{s_{_{NN}}}=200$ GeV Au$+$Au collisions after subtracting an underlying event using a model that includes higher-order azimuthal anisotropy $v_2$, $v_3$, and $v_4$. After subtraction, the away-side ($\Delta\phi\sim\pi)$ of the highest transverse-momentum trigger ($p_T>4$ GeV/$c$) correlations is suppressed compared to that of correlations measured in $p$$+$$p$ collisions. At the lowest associated particle $p_T$, the away-side shape and yield are modified. These observations are consistent with the scenario of radiative-jet energy loss. For the lowest-$p_T$ trigger correlations, an away-side yield exists and we explore the dependence of the shape of the away-side within the context of an underlying-event model. Correlations are also studied differentially versus event-plane angle $\Psi_n$. The angular correlations show an asymmetry when selecting the sign of the trigger-particle azimuthal angle with respect to the $\Psi_2$ event plane. This asymmetry and the measured suppression of the pair yield out of plane is consistent with a path-length-dependent energy loss. No $\Psi_3$ dependence can be resolved within experimental uncertainties.
Higher-order flow harmonics for charged hadrons at midrapidity in Au$+$Au collisions at $\sqrt{s_{NN}}$ and their systematics: $v_2$, $v_3$, $v_4$, and $v_4\{\Psi_2\}$. The source of systematic uncertainties are difference among RXN event-planes, matching cut width for CNT hadron tracks, and difference between $v_n$ measured with RXN and BBC event planes .
Per-trigger yields $Y(\Delta\phi)$ of dihadrons pairs measured in Au$+$Au collisions at$\sqrt{s_{NN}}$ after subtracting the underlying event model with several $p_T$ selections and centralities. Systematic uncertainties are due to track matching and the $v_n$ and due to ZYAM.
Per-trigger yields $Y(\Delta\phi)$ of dihadron pairs measured in Au$+$Au collisions after subtracting the underlying event-model with several $p_T$ selections of the trigger and associated particles ($p_T^{t,a}$ and several centralities. Systematic uncertainties are due to track matching and the $v_n$ and due to ZYAM.
The neutral current e+/-p cross section has been measured up to values of Bjorken x of approximately 1 with the ZEUS detector at HERA using an integrated luminosity of 187 inv. pb of e-p and 142 inv. pb of e+p collisions at sqrt(s) = 318GeV. Differential cross sections in x and Q2, the exchanged boson virtuality, are presented for Q2 geq 725GeV2. An improved reconstruction method and greatly increased amount of data allows a finer binning in the high-x region of the neutral current cross section and leads to a measurement with much improved precision compared to a similar earlier analysis. The measurements are compared to Standard Model expectations based on a variety of recent parton distribution functions.
Double differential cross section for Q^2=725 GeV^2.
Double differential cross section for Q^2=875 GeV^2.
Double differential cross section for Q^2=1025 GeV^2.
The differential cross section for the production of direct photons in p+p collisions at sqrt(s)=200 GeV at midrapidity was measured in the PHENIX detector at the Relativistic Heavy Ion Collider. Inclusive-direct photons were measured in the transverse-momentum range from 5.5--25 GeV/c, extending the range beyond previous measurements. Event structure was studied with an isolation criterion. Next-to-leading-order perturbative-quantum-chromodynamics calculations give a good description of the spectrum. When the cross section is expressed versus x_T, the PHENIX data are seen to be in agreement with measurements from other experiments at different center-of-mass energies.
Cross section of midrapidity inclusive-direct photon production in $p+p$ collisions at $\sqrt{s}$ = 200 GeV as a function of transverse momentum ($p_T$). Asymmetric statistical uncertainties occur in $p_T$ bins with no tagged $π^0$ counts.
Ratio of isolated/inclusive-direct photon (Fig. 13). Upper(+) and lower bounds(-) on systematics can be different, and are listed separately.
Ratio of isolated/inclusive photon from $π^0$ (Fig. 13).
Background: Heavy-flavor production in p+p collisions tests perturbative-quantum-chromodynamics (pQCD) calculations. Modification of heavy-flavor production in heavy-ion collisions relative to binary-collision scaling from p+p results, quantified with the nuclear-modification factor (R_AA), provides information on both cold- and hot-nuclear-matter effects. Purpose: Determine transverse-momentum, pt, spectra and the corresponding R_AA for muons from heavy-flavor mesons decay in p+p and Cu+Cu collisions at sqrt(s_NN)=200 GeV and y=1.65. Method: Results are obtained using the semi-leptonic decay of heavy-flavor mesons into negative muons. The PHENIX muon-arm spectrometers measure the p_T spectra of inclusive muon candidates. Backgrounds, primarily due to light hadrons, are determined with a Monte-Carlo calculation using a set of input hadron distributions tuned to match measured-hadron distributions in the same detector and statistically subtracted. Results: The charm-production cross section in p+p collisions at sqrt{s}=200 GeV, integrated over pt and in the rapidity range 1.4<y<1.9 is found to be dsigma_ccbar/dy = 0.139 +/- 0.029 (stat) ^{+0.051}_{-0.058} (syst) mb. This result is consistent with calculations and with expectations based on the corresponding midrapidity charm-production cross section measured earlier by PHENIX. The R_AA for heavy-flavor muons in Cu+Cu collisions is measured in three centrality intervals for 1<pt<4 GeV/c. Suppression relative to binary-collision scaling (R_AA<1) increases with centrality. Conclusions: Within experimental and theoretical uncertainties, the measured heavy-flavor yield in p+p collisions is consistent with state-of-the-art pQCD calculations. Suppression in central Cu+Cu collisions suggests the presence of significant cold-nuclear-matter effects and final-state energy loss.
Production cross section of negative muons from heavy-flavor mesons decay as a function of $p_T$ in $p$+$p$ collisions at $\sqrt{s}=200$ GeV.
Invariant production yields of negative muons from heavy-flavor-mesons decay as a function $p_T$ in Cu+Cu collisions for three different centrality intervals (40-94%, 20-40%, and 0-20%), scaled by powers of ten for clarity. The solid line associated to each set of points corresponds to a fit to the $p$+$p$ invariant yield distribution described in the text, scaled by the appropriate number of binary collisions $N_{coll}$ when comparing to the Cu+Cu measurements.
Invariant production yields of negative muons from heavy-flavor-mesons decay as a function $p_T$ in $p$+$p$ collisions at $\sqrt{s}=200$ GeV. The solid line associated to each set of points corresponds to a fit to the $p$+$p$ invariant yield distribution described in the text, scaled by the appropriate number of binary collisions $N_{coll}$ when comparing to the Cu+Cu measurements.
First results on inclusive D0 and D* production in deep inelastic $ep$ scattering are reported using data collected by the H1 experiment at HERA in 1994. Differential cross sections are presented for both channels and are found to agree well with QCD predictions based on the boson gluon fusion process. A charm production cross section for 10GeV$~2\le Q~2\le100$GeV$~2$ and $0.01\le y\le0.7$ of $\sigma\left(ep\rightarrow c\overlinecX\right) = (17.4 \pm 1.6 \pm 1.7 \pm 1.4)$nb is derived. A first measurement of the charm contribution F2_charm(x,Q~2) to the proton structure function for Bjorken $x$ between $8\cdot10~{-4}$ and $8\cdot10~{-3}$ is presented. In this kinematic range a ratio F2_charm/F2= 0.237\pm0.021{+0.043\atop-0.039}$ is observed.
Inclusive D meson production cross sections. The second systematc error represents the model uncertainty.
Ratio of cross sections of D0 and D* production.
Normalised and absolute PT distributions. In the absolute cross section the first error includes the independent systematic errors. The first systematic error is the overall systematic error and the second is the overall model dependent error.
Inclusive jet, dijet and trijet differential cross sections are measured in neutral current deep-inelastic scattering for exchanged boson virtualities 150 < Q^2 < 15000 GeV^2 using the H1 detector at HERA. The data were taken in the years 2003 to 2007 and correspond to an integrated luminosity of 351 pb^{-1}. Double differential Jet cross sections are obtained using a regularised unfolding procedure. They are presented as a function of Q^2 and the transverse momentum of the jet, P_T^jet, and as a function of Q^2 and the proton's longitudinal momentum fraction, Xi, carried by the parton participating in the hard interaction. In addition normalised double differential jet cross sections are measured as the ratio of the jet cross sections to the inclusive neutral current cross sections in the respective Q^2 bins of the jet measurements. Compared to earlier work, the measurements benefit from an improved reconstruction and calibration of the hadronic final state. The cross sections are compared to perturbative QCD calculations in next-to-leading order and are used to determine the running coupling and the value of the strong coupling constant as alpha_s(M_Z) = 0.1165 (8)_exp (38)_{pdf,theo}.
Double-differential inclusive jet cross sections measured as a function of Q**2 and PT(JET) using the kT jet algorithm. The total systematic uncertainty sums all systematic uncertainties in quadrature, including the uncertainty due to the LAr noise of 0.5% and the total normalisation uncertainty of 2.9%. The correction factors on the theoretical cross sections C(HAD) and C(EW) are listed in the rightmost columns.
Double-differential dijet cross sections measured as a function of Q**2 and MEAN(PT(2JET)) using the kT jet algorithm. The total systematic uncertainty sums all systematic uncertainties in quadrature, including the uncertainty due to the LAr noise of 0.6% and the total normalisation uncertainty of 2.9%. The correction factors on the theoretical cross sections C(HAD) and C(EW) are listed in the rightmost columns.
Double-differential dijet cross sections measured as a function of Q**2 and XI(2) using the kT jet algorithm. The total systematic uncertainty sums all systematic uncertainties in quadrature, including the uncertainty due to the LAr noise of 0.6% and the total normalisation uncertainty of 2.9%. The correction factors on the theoretical cross sections C(HAD) and C(EW) are listed in the rightmost columns.
The STAR Collaboration reports the measurement of semi-inclusive distributions of charged-particle jets recoiling from a high transverse momentum hadron trigger, in central and peripheral Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV. Charged jets are reconstructed with the anti-kT algorithm for jet radii R between 0.2 and 0.5 and with low infrared cutoff of track constituents ($p_T>0.2$ GeV/c). A novel mixed-event technique is used to correct the large uncorrelated background present in heavy ion collisions. Corrected recoil jet distributions are reported at mid-rapidity, for charged-jet transverse momentum $p_T^\mathrm{jet,ch}<30$ GeV/c. Comparison is made to similar measurements for Pb+Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV, to calculations for p+p collisions at $\sqrt{s}$ = 200 GeV based on the PYTHIA Monte Carlo generator and on a Next-to-Leading Order perturbative QCD approach, and to theoretical calculations incorporating jet quenching. The recoil jet yield is suppressed in central relative to peripheral collisions, with the magnitude of the suppression corresponding to medium-induced charged energy transport out of the jet cone of $2.8\pm0.2\mathrm{(stat)}\pm1.5\mathrm{(sys)}$ GeV/c, for $10<p_T^\mathrm{jet,ch}<20$ GeV/c and R = 0.5. No medium-induced change in jet shape is observed for $R<0.5$. The azimuthal distribution of low-$p_T^\mathrm{jet,ch}$ recoil jets may be enhanced at large azimuthal angles to the trigger axis, due to scattering off quasi-particles in the hot QCD medium. Measurement of this distribution gives a 90% statistical confidence upper limit to the yield enhancement at large deflection angles in central Au+Au collisions of $50\pm30\mathrm{(sys)\%}$ of the large-angle yield in p+pcollisions predicted by PYTHIA.
Distribution of p_{T,jet}^{reco,ch} for Au + Au collisions at \sqrt{s_{NN}} = 200 GeV for R = 0.2 jets in central events.
Distribution of p_{T,jet}^{reco,ch} for Au + Au collisions at \sqrt{s_{NN}} = 200 GeV for R = 0.2 jets in central events, mixed events.
Distribution of p_{T,jet}^{reco,ch} for Au + Au collisions at \sqrt{s_{NN}} = 200 GeV for R = 0.2 jets in peripheral events.
The momentum distribution of electrons from semi-leptonic decays of charm and bottom for mid-rapidity |y|<0.35 in p+p collisions at sqrt(s)=200 GeV is measured by the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) over the transverse momentum range 2 < p_T < 7 GeV/c. The ratio of the yield of electrons from bottom to that from charm is presented. The ratio is determined using partial D/D^bar --> e^{+/-} K^{-/+} X (K unidentified) reconstruction. It is found that the yield of electrons from bottom becomes significant above 4 GeV/c in p_T. A fixed-order-plus-next-to-leading-log (FONLL) perturbative quantum chromodynamics (pQCD) calculation agrees with the data within the theoretical and experimental uncertainties. The extracted total bottom production cross section at this energy is \sigma_{b\b^bar}= 3.2 ^{+1.2}_{-1.1}(stat) ^{+1.4}_{-1.3}(syst) micro b.
Bottom contribution to the electrons from heavy flavor decay as a function of PT. These values has been obtained using g3data software which to extract the data from the plot and should therefore be used with caution. The g3data program indicates an extra uncertainty of 0.01 on these values.
Differential bottom production cross section at mid rapidity (y=0) To obtain this value, the differential "bottom-decay" electrons cross-section has been extrapolated to PT=0 using the spectrum shape predicted by pQCD. The b->e branching ratio used was 10 +-1%.
Invariant cross section of electrons from heavy flavor decay versus PT These values has been obtained using g3data software which to extract the data from the plot and should therefore be used with caution. The values in the last column indicate the level of uncertainty intoduced by g3data.
The exclusive production of $\rho~0$ mesons in deep inelastic electron-proton scattering has been studied using the ZEUS detector. Cross sections have been measured in the range $7 < Q~2 < 25$ GeV$~2$ for $\gamma~*p$ centre of mass (c.m.) energies from 40 to 130 GeV. The $\gamma~*p \rightarrow \rho~0 p$ cross section exhibits a $Q~{-(4.2 \pm 0.8 ~{+1.4}_{-0.5})}$ dependence and both longitudinally and transversely polarised $\rho~0$'s are observed. The $\gamma~*p \rightarrow \rho~0 p$ cross section rises strongly with increasing c.m. energy, when compared with NMC data at lower energy, which cannot be explained by production through soft pomeron exchange. The data are compared with perturbative QCD calculations where the rise in the cross section reflects the increase in the gluon density at low $x$. the gluon density at low $x$.
No description provided.
Elastic $\rho~0$ photoproduction has been measured using the ZEUS detector at HERA. Untagged photoproduction events from $ep$ interactions were used to measure the reaction $\gamma p \rightarrow \rho~0 p$ ($\rho~0 \rightarrow \pi~+ \pi~-$) at photon-proton centre-of-mass energies between 60 and 80GeV and $|t|<0.5$GeV$~2$, where $t$ is the square of the four-momentum transferred at the proton vertex. The differential cross section $d\sigma/dM_{\pi\pi}$, where $M_{\pi\pi}$ is the invariant mass of the two pions, and the integrated cross section, $\sigma_{\gamma p\rightarrow \rho~0 p}$, are presented; the latter was measured to be $14.7\pm 0.4(\mbox{stat.})\pm2.4(\mbox{syst.})\mu\mbox{b}$. The differential cross section $d\sigma/dt$ has an approximately exponential shape; a fit of the type $A~{\prime}_{t} \exp{(-b~{\prime}_{t}|t| + c~{\prime}_{t} t~2)}$ yields a $t$-slope $b~{\prime}_{t}= 9.9\pm1.2(\mbox{stat.})\pm 1.4(\mbox{syst.})\mu\mbox{b}$. The results, when compared to low energy data, show a weak energy dependence of both $\sigma_{\gamma p\rightarrow \rho~0 p}$ and of the $t$-slope. The $\rho~0$ is produced predominantly with transverse polarisation, demonstrating that $s$-channel helicity conservation holds at these energies.
Integrated cross section for exclusive rho0 <pi+ pi-> production where 2Mpi < Mpi pi < Mrho + 5width0.
No description provided.
Applying the Spital and Yennie method to each t bin. No errors given.
We present measurements of elliptic flow ($v_2$) of electrons from the decays of heavy-flavor hadrons ($e_{HF}$) by the STAR experiment. For Au+Au collisions at $\sqrt{s_{\rm NN}} = $ 200 GeV we report $v_2$, for transverse momentum ($p_T$) between 0.2 and 7 GeV/c using three methods: the event plane method ($v_{2}${EP}), two-particle correlations ($v_2${2}), and four-particle correlations ($v_2${4}). For Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 62.4 and 39 GeV we report $v_2${2} for $p_T< 2$ GeV/c. $v_2${2} and $v_2${4} are non-zero at low and intermediate $p_T$ at 200 GeV, and $v_2${2} is consistent with zero at low $p_T$ at other energies. The $v_2${2} at the two lower beam energies is systematically lower than at $\sqrt{s_{\rm NN}} = $ 200 GeV for $p_T < 1$ GeV/c. This difference may suggest that charm quarks interact less strongly with the surrounding nuclear matter at those two lower energies compared to $\sqrt{s_{\rm NN}} = 200$ GeV.
Signal-to-background (S/B) ratio as a function of transverse momentum, Au+Au 200 GeV, 0-60% central events with minimum bias trigger
Signal-to-background (S/B) ratio as a function of transverse momentum, Au+Au 200 GeV, 0-60% central events with with High Tower (high pT) trigger
Signal-to-background (S/B) ratio as a function of transverse momentum, Au+Au 39 GeV, 0-60% central events with minimum bias trigger
The DELPHI detector at LEP has collected 54 pb^{-1} of data at a centre-of-mass energy around 183 GeV during 1997, 158 pb^{-1} around 189 GeV during 1998, and 187 pb^{-1} between 192 and 200 GeV during 1999. These data were used to measure the average charged particle multiplicity in e+e- -> b bbar events, <n>_{bb}, and the difference delta_{bl} between <n>_{bb} and the multiplicity, <n>_{ll}, in generic light quark (u,d,s) events: delta_{bl}(183 GeV) = 4.55 +/- 1.31 (stat) +/- 0.73 (syst) delta_{bl}(189 GeV) = 4.43 +/- 0.85 (stat) +/- 0.61 (syst) delta_{bl}(200 GeV) = 3.39 +/- 0.89 (stat) +/- 1.01 (syst). This result is consistent with QCD predictions, while it is inconsistent with calculations assuming that the multiplicity accompanying the decay of a heavy quark is independent of the mass of the quark itself.
Only statistical errors.
No description provided.
Charm production in deep inelastic ep scattering was measured with the ZEUS detector using an integrated luminosity of 354 pb^{-1}. Charm quarks were identified by reconstructing D^{+} mesons in the D^{+} -> K^{-} pi^{+} pi^{+} decay channel. Lifetime information was used to reduce combinatorial background substantially. Differential cross sections were measured in the kinematic region 5 < Q^{2} < 1000 GeV^{2}, 0.02 < y < 0.7, 1.5 < p_{T}(D^{+}) < 15 GeV and |eta(D^{+})| < 1.6, where Q^{2} is the photon virtuality, y is the inelasticity, and p_{T}(D^{+}) and eta(D^{+}) are the transverse momentum and the pseudorapidity of the D^{+} meson, respectively. Next-to-leading-order QCD predictions are compared to the data. The charm contribution, F_{2}^{cc}, to the proton structure-function F_{2} was extracted.
The bin-averaged differential cross section as a function of Q^2. The (sys) error is the experimental systematic uncertainty, excluding the luminosity and branching ratio uncertainties.
The bin-averaged differential cross section as a function of Y. The (sys) error is the experimental systematic uncertainty, excluding the luminosity and branching ratio uncertainties.
The bin-averaged differential cross section as a function of PT. The (sys) error is the experimental systematic uncertainty, excluding the luminosity and branching ratio uncertainties.
The production of single photons has been studied in the reaction e+e- -> gamma + invisible particles at centre-of-mass energies of 183 GeV and 189 GeV. A previously published analysis of events with multi-photon final states accompanied by missing energy has been updated with 189 GeV data. The data were collected with the DELPHI detector and correspond to integrated luminosities of about 51 pb^{-1} and 158 pb^{-1} at the two energies. The number of light neutrino families is measured to be 2.84 +/- 0.15(stat) +/- 0.14(syst). The absence of an excess of events beyond that expected from Standard Model processes is used to set limits on new physics as described by supersymmetric and composite models. A limit on the gravitational scale is also determined.
No description provided.
Combined result.
New data are presented on charged particle pseudorapidity distributions for inelastic events produced at c.m. energies\(\sqrt s \)=200 and 900 GeV. The data were obtained at the CERN antiproton-proton Collider operated in a new pulsed mode. The rise of the central density ρ(0) at energies up to\(\sqrt s \)=900 GeV has been studied. A new form of central region scaling is found involving the densityρn(0) for charged multiplicityn, namely that the scaled central densityρn(0)/ρ(0) expressed as a function ofz=n/〈n〉 is independent ofs. Scaling in the fragmentation region holds to 10–20%, and the small amount of scalebreaking observed here could be accommodated within the framework suggested by Wdowcyk and Wolfendale to account for both accelerator and cosmic ray data.
.
.
.
A combination is presented of all inclusive deep inelastic cross sections previously published by the H1 and ZEUS collaborations at HERA for neutral and charged current $e^{\pm}p$ scattering for zero beam polarisation. The data were taken at proton beam energies of 920, 820, 575 and 460 GeV and an electron beam energy of 27.5 GeV. The data correspond to an integrated luminosity of about 1 fb$^{-1}$ and span six orders of magnitude in negative four-momentum-transfer squared, $Q^2$, and Bjorken $x$. The correlations of the systematic uncertainties were evaluated and taken into account for the combination. The combined cross sections were input to QCD analyses at leading order, next-to-leading order and at next-to-next-to-leading order, providing a new set of parton distribution functions, called HERAPDF2.0. In addition to the experimental uncertainties, model and parameterisation uncertainties were assessed for these parton distribution functions. Variants of HERAPDF2.0 with an alternative gluon parameterisation, HERAPDF2.0AG, and using fixed-flavour-number schemes, HERAPDF2.0FF, are presented. The analysis was extended by including HERA data on charm and jet production, resulting in the variant HERAPDF2.0Jets. The inclusion of jet-production cross sections made a simultaneous determination of these parton distributions and the strong coupling constant possible, resulting in $\alpha_s(M_Z)=0.1183 \pm 0.0009 {\rm(exp)} \pm 0.0005{\rm (model/parameterisation)} \pm 0.0012{\rm (hadronisation)} ^{+0.0037}_{-0.0030}{\rm (scale)}$. An extraction of $xF_3^{\gamma Z}$ and results on electroweak unification and scaling violations are also presented.
HERA combined reduced cross sections $\sigma_{r,\rm NC}^{+}$ for NC $e^{+}p$ scattering at $\sqrt{s} = 318$ GeV; $\delta_{\rm stat}$, $\delta_{\rm uncor}$ and $\delta_{\rm cor}$ represent the statistical, uncorrelated systematic and correlated systematic uncertainties, respectively; $\delta_{\rm rel}$, $\delta_{\gamma p}$, $\delta_{\rm had}$ and $\delta_{1}$ to $\delta_{4}$ are the correlated sources of uncertainties arising from the combination procedure. The uncertainties are quoted in percent relative to $\sigma_{r,\rm NC}^{+}$.
HERA combined reduced cross sections $\sigma_{r,\rm NC}^{+}$ for NC $e^{+}p$ scattering at $\sqrt{s} = 300$ GeV; $\delta_{\rm stat}$, $\delta_{\rm uncor}$ and $\delta_{\rm cor}$ represent the statistical, uncorrelated systematic and correlated systematic uncertainties, respectively; $\delta_{\rm rel}$, $\delta_{\gamma p}$, $\delta_{\rm had}$ and $\delta_{1}$ to $\delta_{4}$ are the correlated sources of uncertainties arising from the combination procedure. The uncertainties are quoted in percent relative to $\sigma_{r,\rm NC}^{+}$.
HERA combined reduced cross sections $\sigma_{r,\rm NC}^{+}$ for NC $e^{+}p$ scattering at $\sqrt{s} = 251$ GeV; $\delta_{\rm stat}$, $\delta_{\rm uncor}$ and $\delta_{\rm cor}$ represent the statistical, uncorrelated systematic and correlated systematic uncertainties, respectively; $\delta_{\rm rel}$, $\delta_{\gamma p}$, $\delta_{\rm had}$ and $\delta_{1}$ to $\delta_{4}$ are the correlated sources of uncertainties arising from the combination procedure. The uncertainties are quoted in percent relative to $\sigma_{r,\rm NC}^{+}$.
Production of D*+/-(2010) mesons in diffractive deep inelastic scattering has been measured with the ZEUS detector at HERA using an integrated luminosity of 82 pb^{-1}. Diffractive events were identified by the presence of a large rapidity gap in the final state. Differential cross sections have been measured in the kinematic region 1.5 < Q^2 < 200 GeV^2, 0.02 < y < 0.7, x_{IP} < 0.035, beta < 0.8, p_T(D*+/-) > 1.5 GeV and |\eta(D*+/-)| < 1.5. The measured cross sections are compared to theoretical predictions. The results are presented in terms of the open-charm contribution to the diffractive proton structure function. The data demonstrate a strong sensitivity to the diffractive parton densities.
Total cross section for diffractive D*+- production in the stated kinematicregion.. The second DSYS uncertainty arises from the subtraction of the proton-dissociative background.
The differential cross section as a function of X(NAME=POMERON).
The differential cross section as a function of transverse momentum.
Dihadron and isolated direct photon-hadron angular correlations are measured in $p$$+$$p$ collisions at $\sqrt{s}=200$ GeV. The correlations are sensitive to nonperturbative initial-state and final-state transverse momentum $k_T$ and $j_T$ in the azimuthal nearly back-to-back region $\Delta\phi\sim\pi$. In this region, transverse-momentum-dependent evolution can be studied when several different hard scales are measured. To have sensitivity to small transverse momentum scales, nonperturbative momentum widths of $p_{\rm out}$, the out-of-plane transverse momentum component perpendicular to the trigger particle, are measured. These widths are used to investigate possible effects from transverse-momentum-dependent factorization breaking. When accounting for the longitudinal momentum fraction of the away-side hadron with respect to the near-side trigger particle, the widths are found to increase with the hard scale; this is qualitatively similar to the observed behavior in Drell-Yan and semi-inclusive deep-inelastic scattering interactions. The momentum widths are also studied as a function of center-of-mass energy by comparing to previous measurements at $\sqrt{s}=510$ GeV. The nonperturbative jet widths also appear to increase with $\sqrt{s}$ at a similar $x_T$, which is qualitatively consistent to similar measurements in Drell-Yan interactions. To quantify the magnitude of any transverse-momentum-dependent factorization breaking effects, calculations will need to be performed to compare to these measurements.
The per-trigger yields are shown as a function of $\Delta\phi$ in several $p_T^{trig}$ $\otimes$ $p_T^{assoc}$ bins.
The per-trigger yields are shown as a function of $\Delta\phi$ in several $p_T^{trig}$ $\otimes$ $p_T^{assoc}$ bins.
The per-trigger yields are shown as a function of $\Delta\phi$ in several $p_T^{trig}$ $\otimes$ $p_T^{assoc}$ bins.
The e^+p charged-current deep inelastic scattering cross sections, $d\sigma/dQ^2$ for Q^2 between 200 and 60000 GeV^2, and $d\sigma/dx$ and $d\sigma/dy$ for Q^2 > 200 GeV^2, have been measured with the ZEUS detector at HERA. A data sample of 47.7 pb^-1, collected at a center-of-mass energy of 300 GeV, has been used. The cross section $d\sigma/dQ^2$ falls by a factor of about 50000 as Q^2 increases from 280 to 30000 GeV^2. The double differential cross section $d^2\sigma/dxdQ^2$ has also been measured. A comparison between the data and Standard Model (SM) predictions shows that contributions from antiquarks ($\bar{u}$ and $\bar{c}$) and quarks (d and s) are both required by the data. The predictions of the SM give a good description of the full body of the data presented here. A comparison of the charged-current cross section $d\sigma/dQ^2$ with the recent ZEUS results for neutral-current scattering shows that the weak and electromagnetic forces have similar strengths for Q^2 above $M^2_W, M^2_Z$. A fit to the data for $d\sigma/dQ^2$ with the Fermi constant $G_F$ and $M_W$ as free parameters yields $G_F = (1.171 \pm 0.034 (stat.) ^{+0.026}_{-0.032} (syst.) ^{+0.016}_{-0.015} (PDF)) \times 10^{-5} GeV^{-2}$ and $M_W = 80.8 ^{+4.9}_{-4.5} (stat.) ^{+5.0}_{-4.3} (syst.) ^{+1.4}_{-1.3} (PDF) GeV$. Results for $M_W$, where the propagator effect alone or the SM constraint between $G_F$ and $M_W$ have been considered, are also presented.
The differential cross section DSIG/DQ**2.
The differential cross section DSIG/DX.
The differential cross section DSIG/DY.
We present results obtained from a study of the structure of hadronic events recorded by the L3 detector at various centre-of-mass energies. The distributions of event shape variables and the energy dependence of their mean values are measured from 30GeV to 189GeV and compared with various QCD models. The energy dependence of the moments of event shape variables is used to test a power law ansatz for the non-perturbative component. We obtain a universal value of the non-perturbative parameter alpha_0 = 0.537 +/- 0.073. From a comparison with resummed O(alpha_s^2) QCD calculations, we determine the strong coupling constant at each of the selected energies. The measurements demonstrate the running of alpha_s as expected in QCD with a value of alpha_s(m_Z) = 0.1215 +/- 0.0012 (exp) +/- 0.0061 (th).
Distribution for THRUST at c.m. energy 189 GeV.
Distribution for Heavy Jet Mass at c.m. energy 189 GeV.
Distribution for Total Jet Broadening at c.m. energy 189 GeV.
The triple gauge-boson couplings involving the W are determined using data samples collected with the ALEPH detector at mean centre-of-mass energies of 183 GeV and 189 GeV, corresponding to integrated luminosities of 57 pb^-1 and 174 pb^-1, respectively. The couplings, g^Z_1, Kappa_gamma and lambda_gamma, are measured using W-pair events, single-W production and single-gamma production. Each coupling is measured individually with the other two coupling fixed at their Standard Model value. Including ALEPH results from lower energies, the 95% confidence level intervals for the deviation to the Standard Model are -0.087 < Dg^Z_1 < 0.141 -0.200 < DKappa_gamma < 0.258 -0.062 < Lambda_gamma < 0.147. Fits are also presented where two or all three couplings are allowed to vary. In addition, W-pair events are used to set limits on the C- or P-violating couplings g^V_4, g^V_5, Kappa_V, and Lambda_V, where V denotes either gamma or Z. No deviations from the Standard Model expectations are observed.
The errors included the statistical and systematic uncertainties. Deviation from SM values.
The errors included the statistical and systematic uncertainties. Combined results, lower sqrt(s) data are also included.
The errors included the statistical and systematic uncertainties. Combined results, lower sqrt(s) data are also included. Three-parameter fit.
Deep-inelastic ep scattering data, taken with the H1 detector at HERA, are used to study the event shape variables thrust, jet broadening, jet mass, C parameter and two kinds of differential two-jet rate. The data cover a large range of the four-momentum transfer Q, which is considered to be the relevant energy scale, between 7 GeV and 100 GeV. The Q dependences of the mean values are compared with second order calculations of perturbative QCD applying power law corrections proportional to 1/Q^p to account for hadronization effects. The concept of power corrections is investigated by fitting simultaneously a non-perturbative parameter alpha_p and the strong coupling constant alpha_s.
Corrected mean values of the (1-THRUST) distribution (w.r.t.current hemisphere axis) as a function of Q.
Corrected mean values of the Jet Broadenning (B) distribution (w.r.t.current hemisphere axis) as a function of Q.
Corrected mean values of the (1-THRUST) distribution (w.r.t.max long. momentum axis) as a function of Q.
Double-tagged interactions of photons with virtualities Q^2 between 10 GeV^2 and 200 GeV^2 are studied with the data collected by DELPHI at LEPII from 1998 to 2000, corresponding to an integrated luminosity of 550 pb^{-1}. The gam* gam* -> mu+mu- data agree with QED predictions. The cross-section of the reaction gam* gam* -> hadrons is measured and compared to the LO and NLO BFKL calculations.
Measured cross section for the process E+ E- --> E+ E- HADRONS.
Measured cross section for the process GAMMA* GAMMA* --> HADRONS.
Differential cross section for GAMMA* GAMMA* --> MU+ MU-.
No description provided.
No description provided.
No description provided.
Measurements of primary charged hadron multiplicity distributions are presented for non-single-diffractive events in proton-proton collisions at centre-of-mass energies of sqrt(s) = 0.9, 2.36, and 7 TeV, in five pseudorapidity ranges from |eta|<0.5 to |eta|<2.4. The data were collected with the minimum-bias trigger of the CMS experiment during the LHC commissioning runs in 2009 and the 7 TeV run in 2010. The multiplicity distribution at sqrt(s) = 0.9 TeV is in agreement with previous measurements. At higher energies the increase of the mean multiplicity with sqrt(s) is underestimated by most event generators. The average transverse momentum as a function of the multiplicity is also presented. The measurement of higher-order moments of the multiplicity distribution confirms the violation of Koba-Nielsen-Olesen scaling that has been observed at lower energies.
Mean multiplicity for charged hadron production for |pseudorapidity| < 2.4.
Fully corrected charged hadron multiplicity spectrum for |pseudorapidity| < 0.5 at a centre-of-mass energy of 900 GeV.
Fully corrected charged hadron multiplicity spectrum for |pseudorapidity| < 1.0 at a centre-of-mass energy of 900 GeV.
The production of D+- and D0 mesons has been measured with the ZEUS detector at HERA using an integrated luminosity of 133.6 pb-1. The measurements cover the kinematic range 5 < Q^2 < 1000 GeV^2, 0.02 < y < 0.7, 1.5 < p_T^D < 15 GeV and eta^D < 1.6. Combinatorial background to the D meson signals is reduced by using the ZEUS microvertex detector to reconstruct displaced secondary vertices. Production cross sections are compared with the predictions of next-to-leading-order QCD which is found to describe the data well. Measurements are extrapolated to the full kinematic phase space in order to obtain the open-charm contribution, F2^ccbar, to the proton structure function, F2.
Production cross section for (D+ + D-) mesons.
Production cross section for (D0 + DBAR0) mesons not originating from D*+- decays.
Measured D+- cross section as a function of Q**2.
The production of $D^{*\pm}$ mesons in deep inelastic $ep$ scattering has been measured for exchanged photon virtualities $ 5<Q^2<1000 \gev^2 $, using an integrated luminosity of 363 pb$^{-1}$ with the ZEUS detector at HERA. Differential cross sections have been measured and compared to next-to-leading-order QCD calculations. The cross-sections are used to extract the charm contribution to the proton structure functions, expressed in terms of the reduced charm cross section, $\sigma_{\rm red}^{c\bar{c}}$. Theoretical calculations based on fits to inclusive HERA data are compared to the results.
D(SIG)/DPT IN NB/GEV as a function of PT IN GEV.
D(SIG)/DETARAP IN NB as a function of ETARAP.
D(SIG)/DZ IN NB as a function of Z.
We have studied hadronic events from e+e- annihilation data at centre-of-mass energies of sqrt{s}=172, 183 and 189 GeV. The total integrated luminosity of the three samples, measured with the OPAL detector, corresponds to 250 pb^-1. We present distributions of event shape variables, charged particle multiplicity and momentum, measured separately in the three data samples. From these we extract measurements of the strong coupling alpha_s, the mean charged particle multiplicity <nch> and the peak position xi_0 in the xi_p=ln(1/x_p) distribution. In general the data are described well by analytic QCD calculations and Monte Carlo models. Our measured values of alpha_s, <nch> and xi_0 are consistent with previous determinations at sqrt{s}=MZ.
Distribution of Thrust.
Distribution of Thrust Major.
Distribution of Thrust Minor.
Inclusive charged particle and event shape distributions are measured using 321 hadronic events collected with the DELPHI experiment at LEP at effective centre of mass energies of 130 to 136 GeV. These distributions are presented and compared to data at lower energies, in particular to the precise Z data. Fragmentation models describe the observed changes of the distributions well. The energy dependence of the means of the event shape variables can also be described using second order QCD plus power terms. A method independent of fragmentation model corrections is used to determine αs from the energy dependence of the mean thrust and heavy jet mass. It is measured to be: $$←pha _s(133 {⤪ GeV})={0.116}pm {0.007}_{exp-0.004theo}^{+0.005}$$ from the high energy data.
mean values for event shape variables.
Integral of event shape distribution over the specified interval.
Integral of event shape distribution over the specified interval.
Forum