The centrality dependence of the charged-particle multiplicity density at mid-rapidity in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV is presented. The charged-particle density normalized per participating nucleon pair increases by about a factor 2 from peripheral (70-80%) to central (0-5%) collisions. The centrality dependence is found to be similar to that observed at lower collision energies. The data are compared with models based on different mechanisms for particle production in nuclear collisions.
The charged particle multiplicity density measurements for the nine centrality classes. Also given are the mean values of NPART, the number of participating nucleon pairs calulcated fromthe Glauber model. The errors shown are the systematic errors, with the statistical errors being small.
The dependence of the charged particle multiplicity density on the number of participants in the collisions.
A measurement of the cross section for the inclusive production of isolated prompt photons in pp collisions at a centre-of-mass energy sqrt(s) = 7TeV is presented. The measurement covers the pseudorapidity ranges |eta|<1.37 and 1.52<|eta|<1.81 in the transverse energy range 15 < E_T <100 GeV. The results are based on an integrated luminosity of 880 nb-1, collected with the ATLAS detector at the Large Hadron Collider. Photon candidates are identified by combining information from the calorimeters and from the inner tracker. Residual background in the selected sample is estimated from data based on the observed distribution of the transverse isolation energy in a narrow cone around the photon candidate. The results are compared to predictions from next-to-leading order perturbative QCD calculations.
The measured prompt photon cross section as a function of transverse energy for the |pseudorapidity| range < 0.6.
The measured prompt photon cross section as a function of transverse energy for the |pseudorapidity| range 0.6 to 1.37.
The measured prompt photon cross section as a function of transverse energy for the |pseudorapidity| range 1.52 to 1.81.
The production of mesons containing strange quarks (K$^0_s$, $\phi$) and both singly and doubly strange baryons ($\Lambda$, Anti-$\Lambda$, and $\Xi$+Anti-$\Xi$) are measured at central rapidity in pp collisions at $\sqrt{s}$ = 0.9 TeV with the ALICE experiment at the LHC. The results are obtained from the analysis of about 250 k minimum bias events recorded in 2009. Measurements of yields (dN/dy) and transverse momentum spectra at central rapidities for inelastic pp collisions are presented. For mesons, we report yields (
The measured production spectra for K0s hadrons as a function of pT.
The measured production spectra for Lambda hadrons as a function of pT.
The measured production spectra for Anti-Lambda hadrons as a function of pT.
Measurements are presented from proton-proton collisions at centre-of-mass energies of sqrt(s) = 0.9, 2.36 and 7 TeV recorded with the ATLAS detector at the LHC. Events were collected using a single-arm minimum-bias trigger. The charged-particle multiplicity, its dependence on transverse momentum and pseudorapidity and the relationship between the mean transverse momentum and charged-particle multiplicity are measured. Measurements in different regions of phase-space are shown, providing diffraction-reduced measurements as well as more inclusive ones. The observed distributions are corrected to well-defined phase-space regions, using model-independent corrections. The results are compared to each other and to various Monte Carlo models, including a new AMBT1 PYTHIA 6 tune. In all the kinematic regions considered, the particle multiplicities are higher than predicted by the Monte Carlo models. The central charged-particle multiplicity per event and unit of pseudorapidity, for tracks with pT >100 MeV, is measured to be 3.483 +- 0.009 (stat) +- 0.106 (syst) at sqrt(s) = 0.9 TeV and 5.630 +- 0.003 (stat) +- 0.169 (syst) at sqrt(s) = 7 TeV.
Charged-particle multiplicities in proton-proton collisions at a centre-of mass energy of 900 GeV as a function of pseudorapidity for events with the number of charged particles >=1 having transverse momentum >500 MeV and absolute(pseudorapidity) <2.5.
Charged-particle multiplicities in proton-proton collisions at a centre-of mass energy of 2360 GeV as a function of pseudorapidity for events with the number of charged particles >=1 having transverse momentum >500 MeV and absolute(pseudorapidity) <2.5.
Charged-particle multiplicities in proton-proton collisions at a centre-of mass energy of 7000 GeV as a function of pseudorapidity for events with the number of charged particles >=1 having transverse momentum >500 MeV and absolute(pseudorapidity) <2.5.
The differential cross section for the inclusive production of isolated prompt photons has been measured as a function of the photon transverse energy E_T-gamma in pp collisions at sqrt(s)=7 TeV using data recorded by the CMS detector at the LHC. The data sample corresponds to an integrated luminosity of 2.9 inverse picobarns. Photons are required to have a pseudorapidity |eta_gamma|<1.45 and E_T-gamma > 21 GeV, covering the kinematic region 0.006 < x_T < 0.086. The measured cross section is found to be in agreement with next-to-leading-order perturbative QCD calculations.
Measured isolated prompt photon differential cross section.
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 J/psi mesons is studied in pp collisions at sqrt(s)=7 TeV with the CMS experiment at the LHC. The measurement is based on a dimuon sample corresponding to an integrated luminosity of 314 inverse nanobarns. The J/psi differential cross section is determined, as a function of the J/psi transverse momentum, in three rapidity ranges. A fit to the decay length distribution is used to separate the prompt from the non-prompt (b hadron to J/psi) component. Integrated over J/psi transverse momentum from 6.5 to 30 GeV/c and over rapidity in the range |y| < 2.4, the measured cross sections, times the dimuon decay branching fraction, are 70.9 \pm 2.1 (stat.) \pm 3.0 (syst.) \pm 7.8(luminosity) nb for prompt J/psi mesons assuming unpolarized production and 26.0 \pm 1.4 (stat.) \pm 1.6 (syst.) \pm 2.9 (luminosity) nb for J/psi mesons from b-hadron decays.
Total cross section within the kinematic limits for prompt and non-prompt J/PSI production times branching ratio into MU+ MU-, assuming zero polarizartion. The second systematic error is the luminosity uncertainty.
Differential inclusive cross J/PSI section for the |rapidity| range 0 to 1.2 for each prompt J/PSI polarization scenario considered.
Differential inclusive cross J/PSI section for the |rapidity| range 1.2 to 1.6 for each prompt J/PSI polarization scenario considered.
The energy dependence of the photon-proton total cross section, sigma-tot, was determined from ep scattering data collected with the ZEUS detector at HERA at three values of the center-of-mass energy, W, of the gamma-p system in the range 194
Ratios of the cross sections for 3 energy bins. The first DSYS error isthe uncorrelated uncertainty and the second is the correlated uncertainty.
Fitted power law energy dependence.
The production of η mesons in proton-proton collisions has been studied using the WASA detector at the CELSIUS storage ring at excess energies of Q=40 MeV and Q=72 MeV. The η was detected through its 2γ decay in a near-4π electromagnetic calorimeter, whereas the protons were measured by a combination of straw chambers and plastic scintillator planes in the forward hemisphere. About 6.9×104 and 9.3×104 events were found at Q=40 MeV and Q=72 MeV, respectively, with background contributions of less than 5%. A simple parametrization of the production cross section in terms of low partial waves was used to evaluate the acceptance corrections. Strong evidence was found for the influence of higher partial waves. The Dalitz plots show the presence of p waves in both the pp and the η{pp} systems and the angular distributions of the η in the center-of-mass frame suggest the influence of d-wave η mesons.
Differential cross section for pp -> pp eta at proton beam energies of 1360 and 1445 MeV (excess energies of of 40 and 72 MeV). The angle theta* is that between the eta momentum and that of the beam in the overall CM system. The error shown in the table is the combined statistical and systematic uncertainty, excluding the overall normalization error.
Differential cross section for pp -> pp eta at proton beam energies of 1360 and 1445 MeV (excess energies of of 40 and 72 MeV). The angle theta** is that between the pp relative momentum and that of the eta in the diproton rest frame. The error shown in the table is the combined statistical and systematic uncertainty, excluding the overall normalization error.
Differential cross section for pp -> pp eta at a proton beam energy of 1360 MeV (excess energy Q = 40 MeV) with respect to the square of the final pp invariant mass. Note the change in units with respect to the figure.
We report the first measurement of the differential cross section on $\phi$-meson photoproduction from deuterium near the production threshold for a proton using the CLAS detector and a tagged-photon beam in Hall B at Jefferson Lab. The measurement was carried out by a triple coincidence detection of a proton, $K^+$ and $K^-$ near the theoretical production threshold of 1.57 GeV. The extracted differential cross sections $\frac{d\sigma}{dt}$ for the initial photon energy from 1.65-1.75 GeV are consistent with predictions based on a quasifree mechanism. This experiment establishes a baseline for a future experimental search for an exotic $\phi$-N bound state from heavier nuclear targets utilizing subthreshold/near-threshold production of $\phi$ mesons.
Differential cross section as a function of ABS(T-TMIN).
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