Date

Observation of an energy-dependent difference in elliptic flow between particles and anti-particles in relativistic heavy ion collisions

The STAR collaboration Adamczyk, L. ; Adkins, J.K. ; Agakishiev, G. ; et al.
Phys.Rev.Lett. 110 (2013) 142301, 2013.
Inspire Record 1210463 DOI 10.17182/hepdata.102939

Elliptic flow ($v_{2}$) values for identified particles at mid-rapidity in Au+Au collisions, measured by the STAR experiment in the Beam Energy Scan at RHIC at $\sqrt{s_{NN}}=$ 7.7--62.4 GeV, are presented. A beam-energy dependent difference of the values of $v_{2}$ between particles and corresponding anti-particles was observed. The difference increases with decreasing beam energy and is larger for baryons compared to mesons. This implies that, at lower energies, particles and anti-particles are not consistent with the universal number-of-constituent-quark (NCQ) scaling of $v_{2}$ that was observed at $\sqrt{s_{NN}}=$ 200 GeV.

99 data tables

The elliptic flow $v_{2}$ of protons and anti-protons as a function of the transverse momentum, $p_{T}$, for 0–80$\%$ central Au+Au collisions. The lower panels show the difference in $v_{2}(p_{T})$ between the particles and anti-particles. The solid curves are fits with a horizontal line. The shaded areas depict the magnitude of the systematic errors.

The elliptic flow $v_{2}$ of protons and anti-protons as a function of the transverse momentum, $p_{T}$, for 0–80$\%$ central Au+Au collisions. The lower panels show the difference in $v_{2}(p_{T})$ between the particles and anti-particles. The solid curves are fits with a horizontal line. The shaded areas depict the magnitude of the systematic errors.

The elliptic flow $v_{2}$ of protons and anti-protons as a function of the transverse momentum, $p_{T}$, for 0–80$\%$ central Au+Au collisions. The lower panels show the difference in $v_{2}(p_{T})$ between the particles and anti-particles. The solid curves are fits with a horizontal line. The shaded areas depict the magnitude of the systematic errors.

More…

System Size Dependence of Transverse Momentum Correlations at RHIC

The STAR collaboration Adamczyk, L. ; Adkins, J.K. ; Agakishiev, G. ; et al.
Phys.Rev.C 87 (2013) 064902, 2013.
Inspire Record 1216565 DOI 10.17182/hepdata.103060

We present a study of the average transverse momentum ($p_t$) fluctuations and $p_t$ correlations for charged particles produced in Cu+Cu collisions at midrapidity for $\sqrt{s_{NN}} =$ 62.4 and 200 GeV. These results are compared with those published for Au+Au collisions at the same energies, to explore the system size dependence. In addition to the collision energy and system size dependence, the $p_t$ correlation results have been studied as functions of the collision centralities, the ranges in $p_t$, the pseudorapidity $\eta$, and the azimuthal angle $\phi$. The square root of the measured $p_t$ correlations when scaled by mean $p_t$ is found to be independent of both colliding beam energy and system size studied. Transport-based model calculations are found to have a better quantitative agreement with the measurements compared to models which incorporate only jetlike correlations.

17 data tables

Event-by-event $\langle p_{t}\rangle$ distributions for data and mixed events in central Cu+Cu collisions at $\sqrt{s_{NN}}$ = 200 and 62.4 GeV.

Comparison of dynamical $\langle p_{t}\rangle$ fluctuations in Au+Au and Cu+Cu collisions at $\sqrt{s_{NN}}$ = 62.4 and 200 GeV as a function of the number of participanting nucleons.

Comparison of dynamical $\langle p_{t}\rangle$ fluctuations in Au+Au and Cu+Cu collisions at $\sqrt{s_{NN}}$ = 62.4 and 200 GeV as a function of the number of participanting nucleons.

More…

Exclusive $J/\psi$ and $\psi(2S)$ production in $pp$ collisions at $\sqrt{s}=7$ TeV

The LHCb collaboration Aaij, R ; Abellan Beteta, C ; Adametz, A ; et al.
J.Phys.G 40 (2013) 045001, 2013.
Inspire Record 1216886 DOI 10.17182/hepdata.66871

Exclusive $J/\psi$ and $\psi(2S)$ vector meson production has been observed in the dimuon channel using the LHCb detector. The cross-section times branching fractions to two muons with pseudorapidities between 2.0 and 4.5 are measured to be \begin{equation*} \sigma_{pp\rightarrow J/\psi (\rightarrow \mu^{+} \mu^{-})} (2.0 <\eta_{\mu^{\pm}}< 4.5) = 307 \pm 21 \pm 36~\text{pb}, \end{equation*} \begin{equation*} \sigma_{pp\rightarrow \psi(2S) (\rightarrow \mu^{+} \mu^{-})} (2.0 <\eta_{\mu^{\pm}}< 4.5) = 7.8 \pm 1.3 \pm 1.0~\text{pb}, \end{equation*} where the first uncertainties are statistical and the second are systematic. The measurements are found to be in good agreement with results from previous experiments and theoretical predictions. The $J/\psi$ photoproduction cross-section has been measured as a function of the photon-proton centre-of-mass energy. The results are consistent with measurements obtained at HERA and confirm a similar power law behaviour for the photoproduction cross-section.

2 data tables

Cross section times branching ratio to two muons with pseudorapidities between 2.0 and 4.5.

Cross-section measurements (nb) as a function of $J/\psi$ rapidity.


Study of e+e- --> p anti-p via initial-state radiation at BABAR

The BaBar collaboration Lees, J.P. ; Poireau, V. ; Tisserand, V. ; et al.
Phys.Rev.D 87 (2013) 092005, 2013.
Inspire Record 1217421 DOI 10.17182/hepdata.62678

The process e+e- --> p anti-p gamma is studied using 469 fb-1 of integrated luminosity collected with the BABAR detector at the PEP-II collider, at an e+e- center-of-mass energy of 10.6 GeV. From the analysis of the p anti-p invariant mass spectrum, the energy dependence of the cross section for e+e- --> p anti-p is measured from threshold to 4.5 GeV. The energy dependence of the ratio of electric and magnetic form factors, |G_E/G_M|, and the asymmetry in the proton angular distribution are measured for p anti-p masses below 3 GeV. We also measure the branching fractions for the decays J/psi --> p anti-p and psi(2S) --> p anti p.

1 data table

Measurement of the cross section as a function of the invariant mass of the PBAR-P system and the effective form factor for the reaction E+ E- --> PBAR P. The contributions from J/PSI and PSI(25) decaying to PBAR-P have been subtracted. The form factor error is the combined statistical and systematic.


Measurement of Charged Particle Spectra in Deep-Inelastic ep Scattering at HERA

The H1 collaboration Alexa, C. ; Andreev, V. ; Baghdasaryan, A. ; et al.
Eur.Phys.J.C 73 (2013) 2406, 2013.
Inspire Record 1217865 DOI 10.17182/hepdata.62615

Charged particle production in deep-inelastic ep scattering is measured with the H1 detector at HERA. The kinematic range of the analysis covers low photon virtualities, 5

36 data tables

Charged particle density as a function of pseudorapidity for the PT range 0-1 GeV in the HCM frame.

Charged particle density as a function of pseudorapidity for the PT range 1-10 GeV in the HCM frame.

Charged particle density as a function of pseudorapidity for the PT interval 0-1 GeV in fixed Q**2 and X intervals in the HCM frame.

More…

Prompt charm production in pp collisions at sqrt(s)=7 TeV

The LHCb collaboration Aaij, R ; Abellan Beteta, C ; Adametz, A ; et al.
Nucl.Phys.B 871 (2013) 1-20, 2013.
Inspire Record 1218996 DOI 10.17182/hepdata.60321

Charm production at the LHC in pp collisions at sqrt(s)=7 TeV is studied with the LHCb detector. The decays D0 -> K- pi+, D+ -> K- pi+ pi+, D*+ -> D0(K- pi+) pi+, D_s+ -> phi(K- K+) pi+, Lambda_c+ -> p K- pi+, and their charge conjugates are analysed in a data set corresponding to an integrated luminosity of 15 nb^{-1}. Differential cross-sections dsigma/dp_T are measured for prompt production of the five charmed hadron species in bins of transverse momentum and rapidity in the region 0 < p_T < 8 GeV/c and 2.0 < y < 4.5. Theoretical predictions are compared to the measured differential cross-sections. The integrated cross-sections of the charm hadrons are computed in the above p_T-y range, and their ratios are reported. A combination of the five integrated cross-section measurements gives sigma(c\bar{c})_{p_T < 8 GeV/c, 2.0 < y < 4.5} = 1419 +/- 12 (stat) +/- 116 (syst) +/- 65 (frag) microbarn, where the uncertainties are statistical, systematic, and due to the fragmentation functions.

7 data tables

Differential production cross-sections with respect to transverse momentum, dsigma / dp_T, of Lambda_c+ baryons or their charge conjugates in proton-proton collisions at center-of-mass (CM) energy sqrt(s) = 7 TeV. Measured in bins of hadron transverse momentum (p_T) and rapidity (y) with respect to the beam axis, where p_T and y are measured in the CM frame. Contributions of charm hadrons from the decays of b-hadrons have been removed.

Differential production cross-sections with respect to transverse momentum, dsigma / dp_T, of D0 mesons or their charge conjugates in proton-proton collisions at center-of-mass (CM) energy sqrt(s) = 7 TeV. Measured in bins of hadron transverse momentum (p_T) and rapidity (y) with respect to the beam axis, where p_T and y are measured in the CM frame. Contributions of charm hadrons from the decays of b-hadrons have been removed.

Differential production cross-sections with respect to transverse momentum, dsigma / dp_T, of D+ mesons or their charge conjugates in proton-proton collisions at center-of-mass (CM) energy sqrt(s) = 7 TeV. Measured in bins of hadron transverse momentum (p_T) and rapidity (y) with respect to the beam axis, where p_T and y are measured in the CM frame. Contributions of charm hadrons from the decays of b-hadrons have been removed.

More…

Freeze-out Dynamics via Charged Kaon Femtoscopy in sqrt(sNN)=200 GeV Central Au+Au Collisions

The STAR collaboration Adamczyk, L. ; Adkins, J.K. ; Agakishiev, G. ; et al.
Phys.Rev.C 88 (2013) 034906, 2013.
Inspire Record 1219133 DOI 10.17182/hepdata.97126

We present measurements of three-dimensional correlation functions of like-sign low transverse momentum kaon pairs from sqrt(sNN)=200 GeV Au+Au collisions. A Cartesian surface-spherical harmonic decomposition technique was used to extract the kaon source function. The latter was found to have a three-dimensional Gaussian shape and can be adequately reproduced by Therminator event generator simulations with resonance contributions taken into account. Compared to the pion one, the kaon source function is generally narrower and does not have the long tail along the pair transverse momentum direction. The kaon Gaussian radii display a monotonic decrease with increasing transverse mass m_T over the interval of 0.55<=m_T<=1.15 GeV/c^2. While the kaon radii are adequately described by the m_T-scaling in the outward and sideward directions, in the longitudinal direction the lowest m_T value exceeds the expectations from a pure hydrodynamical model prediction.

4 data tables

Independent correlation moments Rl(q) for orders l = 0,2,4 for midrapidity, low transverse momentum kaon pairs from the 20% most central Au+Au collisions at sqrt(sNN)=200 GeV

Kaon correlation function profiles for midrapidity, low transverse momentum kaon pairs from the 20% most central Au+Au collisions at sqrt(sNN)=200 GeV

Kaon source function profiles extracted from the data

More…

Fluctuations of charge separation perpendicular to the event plane and local parity violation in sqrt(sNN)=200 GeV Au+Au collisions at RHIC

The STAR collaboration Adamczyk, L. ; Adkins, J.K. ; Agakishiev, G. ; et al.
Phys.Rev.C 88 (2013) 064911, 2013.
Inspire Record 1219828 DOI 10.17182/hepdata.98967

Previous experimental results based on data (15 million events) collected by the STAR detector at RHIC suggest event-by-event charge separation fluctuations perpendicular to the event plane in non-central heavy-ion collisions. Here we present the correlator previously used split into its two component parts to reveal correlations parallel and perpendicular to the event plane. The results are from a high statistics 200 GeV Au+Au collisions data set (57 million events) collected by the STAR experiment. We explicitly count units of charge separation from which we find clear evidence for more charge separation fluctuations perpendicular than parallel to the event plane. We also employ a modified correlator to study the possible P-even background in same and opposite charge correlations, and find that the P-even background may largely be explained by momentum conservation and collective motion.

10 data tables

(Color online) $\Delta RMS^{\Delta Q}/\langle RMS^{\Delta Q}\rangle$ versus centrality for Au+Au collisions at $\sqrt{s_{NN}}$= 200 GeV. Not corrected for event plane resolution. Errors are statistical only.

(Color online) $\langle sin(\phi_{\alpha} − \Psi_{1})\rangle$ for positive and negative charges versus centrality for Au+Au collisions at $\sqrt{s_{NN}}$= 200 GeV. Shaded area represents the systematic uncertainty for both charge types obtained by comparing correlations from positive and negative pseudorapidity.

(Color online) Three-point correlator, Eq. 1, measured with $1^{st}$ and $2^{nd}$ harmonic event planes versus centrality for Au+Au collisions at $\sqrt{s_{NN}}$= 200 GeV. Shown with crosses are our previous results from the 2004 RHIC run (Y4) [9, 10]. The Y4 run used a second harmonic event plane. Y4 and Y7 $\Psi_{2}$ results are consistent within statistical errors. Shaded areas for the $2^{nd}$ harmonic points represent the systematic uncertainty of the event plane determination. Systematic uncertainties for the $1^{st}$ harmonic points are negligible compared to the statistical ones shown.

More…

Measurement of $D^\pm$ production in deep inelastic $ep$ scattering with the ZEUS detector at HERA

The ZEUS collaboration Abt, I. ; Adamczyk, L. ; Adamus, M. ; et al.
JHEP 05 (2013) 023, 2013.
Inspire Record 1220382 DOI 10.17182/hepdata.62364

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.

12 data tables

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.

More…

Jet-Hadron Correlations in sqrt{s_{NN}} = 200 GeV Au+Au and p+p Collisions

The STAR collaboration Adamczyk, L. ; Adkins, J.K. ; Agakishiev, G. ; et al.
Phys.Rev.Lett. 112 (2014) 122301, 2014.
Inspire Record 1221099 DOI 10.17182/hepdata.89880

Azimuthal angular correlations of charged hadrons with respect to the axis of a reconstructed (trigger) jet in Au+Au and p+p collisions at $\sqrt{s_{\text{NN}}} = 200 \text{GeV}$ in STAR are presented. The trigger jet population in Au+Au collisions is biased towards jets that have not interacted with the medium, allowing easier matching of jet energies between Au+Au and p+p collisions while enhancing medium effects on the recoil jet. The associated hadron yield of the recoil jet is significantly suppressed at high transverse momentum ($p_{\text{T}}^{\text{assoc}}$) and enhanced at low $p_{\text{T}}^{\text{assoc}}$ in 0-20% central Au+Au collisions compared to p+p collisions, which is indicative of medium-induced parton energy loss in ultrarelativistic heavy-ion collisions.

10 data tables

Jet-hadron correlations after background subtraction. Shown with Gaussian fits to jet peaks and systematic uncertanty bands Au+Au(0.5-1 GeV).

Jet-hadron correlations after background subtraction. Shown with Gaussian fits to jet peaks and systematic uncertanty bands p+p(0.5-1).

Jet-hadron correlations after background subtraction. Shown with Gaussian fits to jet peaks and systematic uncertanty bands Au+Au(4-6 GeV).

More…