The cross-section for prompt antiproton production in collisions of protons with an energy of $6.5$ TeV incident on helium nuclei at rest is measured with the LHCb experiment from a data set corresponding to an integrated luminosity of $0.5\,nb^{-1}$. The target is provided by injecting helium gas into the LHC beam line at the LHCb interaction point. The reported results, covering antiproton momenta between $12$ and $110\,\mathrm{GeV/}c$, represent the first direct determination of the antiproton production cross-section in ${\rm p He}$ collisions, and impact the interpretation of recent results on antiproton cosmic rays from space-borne experiments.
Double-differential cross-section in antiproton momentum and transverse momentum for antiproton production in collisions of 6.5 TeV protons on He nuclei at rest. The antiproton momentum is defined in the laboratory frame. Results are averaged over the given kinematic range of each bin. The uncertainty is split into an uncertainty delta_uncorr, uncorrelated among the kinematic bins, and an uncertainty delta_corr, fully correlated among the kinematic bins. For both uncertainties, the systematic uncertainty, dominant for most bins, and the statistical uncertainty, are added in quadrature. The average value within each bin is also reported for the antiproton momentum, the transverse momentum, and x-Feynman xF=2 p_Z*/SQRT(S), where p_Z* is the longitudinal antiproton momentum in the center-of-mass system and SQRT(S) the nucleon-nucleon center-of-mass energy. These average values are obtained from simulation (based on EPOS LHC), to avoid biases from reconstruction effects and given the good agreement with data observed for the simulated kinematic spectra.
Double-differential cross-section in antiproton momentum and transverse momentum for antiproton production in collisions of 6.5 TeV protons on He nuclei at rest. The antiproton momentum is defined in the laboratory frame. Results are averaged over the given kinematic range of each bin. The uncertainty is split into an uncertainty delta_uncorr, uncorrelated among the kinematic bins, and an uncertainty delta_corr, fully correlated among the kinematic bins. For both uncertainties, the systematic uncertainty, dominant for most bins, and the statistical uncertainty, are added in quadrature. The average value within each bin is also reported for the antiproton momentum, the transverse momentum, and x-Feynman xF=2 p_Z*/SQRT(S), where p_Z* is the longitudinal antiproton momentum in the center-of-mass system and SQRT(S) the nucleon-nucleon center-of-mass energy. These average values are obtained from simulation (based on EPOS LHC), to avoid biases from reconstruction effects and given the good agreement with data observed for the simulated kinematic spectra.
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 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.
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.
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.
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.
Using the UA2 apparatus, the inclusive cross section has been measured for production of high- p T direct photons in p̄p collisions at s =546 GeV and s =630 GeV . The results are in good agreement with QCD predictions.
No description provided.
No description provided.
A study ofW± andZ0 properties has been performed using the UA2 detector at the\(\bar pp\) collider. The data correspond to a total integrated luminosity of 142 nb−1 at\(\sqrt s \)=546 GeV, and of 310 nb−1 at\(\sqrt s \)=630 GeV. The experimental results are compared with the predictions of the Standard Model of the unified electroweak theory.
No description provided.
No description provided.
No description provided.
The production of very large transverse momentum ( p T ) hadron jets has been measured in the UA2 experiment at the CERN p p Collider for s =630 GeV . The inclusive jet production cross sections exhibit a p T -dependent increase with respect to the s =546 GeV data from previous Collider runs. This increase can be described both by QCD calculations and by approximate x T =2 p T /√ s scaling. No significant deviation of the data from QCD predictions is observed at very large p T , placing a lower limit on the characteristic scale Λ c of a hypothetical superstrong contact interaction responsible for the binding of preons in the quark ( Λ c >370 GeV at 95% CL).
No description provided.
Inclusive particle production cross-sections have been measured at the\(Sp\bar pS\) collider using the UA2 detector in various ranges of transverse momentum (PT) and pseudo-rapidity (η). Cross-section measurements are presented forπ0 production (PT≦15 GeV/c, |η|≦0.85 andPT≦40 GeV/c, 1.0≦|η|≦1.8), for η meson production (3≦PT≦6 GeV/c, |η|≦0.85) and for charged particle production (PT≦10 GeV/c, 1.0≦|η|≦1.8). Results are compared with the predictions of QCD calculations.
No description provided.
No description provided.
No description provided.
Jet production properties at s = 540 GeV have been measured in the UA2 detector at the CERN p p Collider. Results on the total transverse momentum of the jet system, on the parton density in the nucleon (structure function) and on the two-jet angular distributions are reported. The data are compared with QCD predictions and extrapolations from lower energy experiments.
DISTRIBUTION OF THE SCATTERING ANGLE OF THE 2-JET AXIS IN THE 2-JET COM FRAME WITH A NORMALISATION FIXED AT 1 FOR COS(THETA*) = 0.
STRUCTURE FUNCTION IS DEFINED AS F(X) WHERE D3(SIG)/DX1/DX2/DCOS(THETA) = (F(X1)/X1)*(F(X2)/X2)*D(SIG)/DCOS(THETA).
The production of electrons with very high transverse momentum has been studied in the UA2 experiment at the CERN\(\bar pp\) collider (\(\sqrt s\)=540 GeV). From a sample of events containing an electron candidate withpT>15 GeV/c, we extract a clear signal resulting from the production of the charged intermediate vector bosonW±, which subsequently decays into an electron and a neutrino. We study theW production and decay properties. Further-more, we refine our results on the production and decay of the neutral vector bosonZ0. Finally, we compare the experimental results to the predictions of the standard model of the unified electro-weak theory.
No description provided.
The production of very large transverse momentum hadron jets has been measured in the UA2 experiment at the CERN p p Collider for s = 540 GeV using a highly segmented calorimeter. The range of previously available cross sections for inclusive jet production is extended to p T = 150 GeV and the two-jet invariant mass distribution to m jj = 280 GeV with the largely increased data sample collected during the 1983 running period. The results are compared with the predictions of QCD models.
LISTED ERRORS INCLUDE STATISTICAL AND THE PT-DEPENDENT UNCERTAINTIES. THE ADDITIONAL OVERALL SYSTEMATIC UNCERTAINTY IS 45PCT.
LISTED ERRORS INCLUDE STATISTICAL AND THE M-DEPENDENT UNCERTAINTIES. THE ADDITIONAL OVERALL SYSTEMATIC UNCERTAINTY IS 45PCT.
The production and properties of high transverse momentum hadron jets have been measured in the UA2 experiment at the CERN\(\bar pp\) Collider\((\sqrt s= 540 GEV)\) using a highly segmented total absorption calorimeter. The characteristics of a sample of two-jet events with invariant mass up to 200 GeV/c2 are discussed, including measurements of their fragmentation properties, angular and rapidity distributions, and the properties of the additional energy clusters accompanying the two-jet system. Cross sections for inclusive jet production in the jet transverse momentum range between 30 and 100 GeV/c and for the two-jet invariant mass distribution in the mass range from 60–200 GeV/c2 are reported.
No description provided.
Transverse momentum distributions of pions, kaons and protons have been measured around 90° in the UA2 detector at the SPS p p collider, at a CM energy of 540 GeV. All the cross sections have increased by more than a factor of 2 over those measured at ISR energies and exhibit a flatter behaviour with respect to transverse momentum.
No description provided.
The distribution of total tranverse energy ΣE T over the pseudorapidity interval −1 < η < 1 and an azimuthal range Δφ =300° has been measured in the UA2 experiment at the CERN p p collider ( s = 540 GeV ) using a highly segmented total absorption caloriter. In the events with very large ΣE T (ΣE T ⪆60 GeV ) most of the transverse energy is found to be contained in small angular regions as expected for high transverse momentum hadron jets. We discuss the properties of a sample of two-jet events with invariant two-jet masses up to 140 GeV c 2 and we measure the cross section for inclusive jet production in the range of jet transverse momenta between 15 and 60 GeV c .
No description provided.
HERE ET IS ACTUALLY THE ENERGY-DENSITY=ET/DELTA OMEGA.
No description provided.
Inclusive π 0 production has been measured at the CERN pp̄ collider, s =540 GeV , for 90° production angle and in a range of transverse momenta between 1.5 and 4.5 GeV/ c . The invariant production cross section is larger than that measured at s = 53 GeV for p-p collisions. The production of μ mesons aand of direct photons is also investigated.
No description provided.
The production of electron-positron pairs of masses below 1200 MeV/ c 2 and of transverse momentum above 1.8 GeV/ c has been studied in pp collisions at √ s = 53 and 63 GeV. The cross section for ϱ, ω, and φ production are presented. The continuum below 600 MeV/ c 2 is consistent with origination from Dalitz decays of η and ω mesons and from semileptonic decay of D and D mesons.
No description provided.
Forum