The measurements of particle multiplicity distributions have generated considerable interest in understanding the fluctuations of conserved quantum numbers in the Quantum Chromodynamics (QCD) hadronization regime, in particular near a possible critical point and near the chemical freeze-out. We report the measurement of efficiency and centrality bin width corrected cumulant ratios ($C_{2}/C_{1}$, $C_{3}/C_{2}$) of net-$\Lambda$ distributions, in the context of both strangeness and baryon number conservation, as a function of collision energy, centrality and rapidity. The results are for Au + Au collisions at five beam energies ($\sqrt{s_{NN}}$ = 19.6, 27, 39, 62.4 and 200 GeV) recorded with the Solenoidal Tracker at RHIC (STAR). We compare our results to the Poisson and negative binomial (NBD) expectations, as well as to Ultra-relativistic Quantum Molecular Dynamics (UrQMD) and Hadron Resonance Gas (HRG) model predictions. Both NBD and Poisson baselines agree with data within the statistical and systematic uncertainties. The ratios of the measured cumulants show no features of critical fluctuations. The chemical freeze-out temperatures extracted from a recent HRG calculation, which was successfully used to describe the net-proton, net-kaon and net-charge data, indicate $\Lambda$ freeze-out conditions similar to those of kaons. However, large deviations are found when comparing to temperatures obtained from net-proton fluctuations. The net-$\Lambda$ cumulants show a weak, but finite, dependence on the rapidity coverage in the acceptance of the detector, which can be attributed to quantum number conservation.
Centrality dependence of single cumulants C1, of net-lambda multiplicity distributions at Au + Au collision 19.6 GeV. Values are shown with NBD, Poisson and UrQMD predictions. Npart values are from Phys. Rev. C 104, 024902 (2021) and they are little different than the values shown in the original paper.
Centrality dependence of single cumulants C1, of net-lambda multiplicity distributions at Au + Au collision 27 GeV. Values are shown with NBD, Poisson and UrQMD predictions.Npart values are from Phys. Rev. C 104, 024902 (2021) and they are little different than the values shown in the original paper.
Centrality dependence of single cumulants C1, of net-lambda multiplicity distributions at Au + Au collision 39 GeV. Values are shown with NBD, Poisson and UrQMD predictions.Npart values are from Phys. Rev. C 104, 024902 (2021) and they are little different than the values shown in the original paper.
The NA61/SHINE experiment at the CERN SPS is performing a uniqe study of the phase diagram of strongly interacting matter by varying collision energy and nuclear mass number of colliding nuclei. In central Pb+Pb collisions the NA49 experiment found structures in the energy dependence of several observables in the CERN SPS energy range that had been predicted for the transition to a deconfined phase. New measurements of NA61/SHINE find intriguing similarities in p+p interactions for which no deconfinement transition is expected at SPS energies. Possible implications will be discussed.
K+/PI+ at y=0.
K+/PI+ at y=0.
<K+>/<PI+>.
Flavour inclusive, udsc and b fragmentation functions in unbiased jets, and flavour inclusive, udsc, b and gluon fragmentation functions in biased jets are measured in e+e- annihilations from data collected at centre-of-mass energies of 91.2, and 183-209 GeV with the OPAL detector at LEP. The unbiased jets are defined by hemispheres of inclusive hadronic events, while the biased jet measurements are based on three-jet events selected with jet algorithms. Several methods are employed to extract the fragmentation functions over a wide range of scales. Possible biases are studied in the results are obtained. The fragmentation functions are compared to results from lower energy e+e- experiments and with earlier LEP measurements and are found to be consistent. Scaling violations are observed and are found to be stronger for the fragmentation functions of gluon jets than for those of quarks. The measured fragmentation functions are compared to three recent theoretical next-to-leading order calculations and to the predictions of three Monte Carlo event generators. While the Monte Carlo models are in good agreement with the data, the theoretical predictions fail to describe the full set of results, in particular the b and gluon jet measurements.
The udsc jet fragmentation function in bins of $x_{\rm E}$ and scale. The scale denotes $Q_{\rm jet}$ for the biased jets and is given by the intervals, while it denotes $\sqrt{s}/2$ for the unbiased jets and is given by the single values. These data are displayed in Fig.7.
The b jet fragmentation function in bins of $x_{\rm E}$ and scale. The scale denotes $Q_{\rm jet}$ for the biased jets and is given by the intervals, while it denotes $\sqrt{s}/2$ for the unbiased jets and is given by the single values. These data are displayed in Fig. 8. In the region 0.48 $<x_{\rm E}<$ 0.90 and $Q_{\rm jet}=$ 30-70 GeV, no measurement was possible due to low statistics.
The gluon jet fragmentation functions in bins of $x_{\rm E}$ and scale $Q_{\rm jet}$ obtained from the biased jets using the b-tag method (BT). These data are displayed in Fig. 9. In the region 0.48 $<x_{\rm E}<$ 0.90 and $Q_{\rm jet}=$ 30-42 GeV for the b-tag method, no measurement was possible due to low statistics.
The exclusive electroproduction of J/psi mesons, ep->epJ/psi, has been studied with the ZEUS detector at HERA for virtualities of the exchanged photon in the ranges 0.15<Q^2<0.8 GeV^2 and 2<Q^2<100 GeV^2 using integrated luminosities of 69 pb^-1 and 83 pb^-1, respectively.The photon-proton centre-of-mass energy was in the range 30<W<220 GeV and the squared four-momentum transfer at the proton vertex |t|<1.The cross sections and decay angular distributions are presented as functions of Q^2, W and t. The effective parameters of the Pomeron trajectory are in agreement with those found in J/psi photoproduction. The spin-density matrix elements, calculated from the decay angular distributions, are consistent with the hypothesis of s-channel helicity conservation. The ratio of the longitudinal to transverse cross sections, sigma_L/sigma_T, grows with Q^2, whilst no dependence on W or t is observed. The results are in agreement with perturbative QCD calculations and exhibit a strong sensitivity to the gluon distribution in the proton.
Cross sections for exclusive J/PSI production as a function of W in the Q**2 region 0.15 to 0.18 GeV**2.
Cross sections for exclusive J/PSI production as a function of W in the Q**2 region 2 to 5 GeV**2.
Cross sections for exclusive J/PSI production as a function of W in the Q**2 region 5 to 10 GeV**2.
The acceptance-corrected dielectron excess mass spectra, where the known hadronic sources have been subtracted from the inclusive dielectron mass spectra, are reported for the first time at mid-rapidity $|y_{ee}|<1$ in minimum-bias Au+Au collisions at $\sqrt{s_{NN}}$ = 19.6 and 200 GeV. The excess mass spectra are consistently described by a model calculation with a broadened $\rho$ spectral function for $M_{ee}<1.1$ GeV/$c^{2}$. The integrated dielectron excess yield at $\sqrt{s_{NN}}$ = 19.6 GeV for $0.4<M_{ee}<0.75$ GeV/$c^2$, normalized to the charged particle multiplicity at mid-rapidity, has a value similar to that in In+In collisions at $\sqrt{s_{NN}}$ = 17.3 GeV. For $\sqrt{s_{NN}}$ = 200 GeV, the normalized excess yield in central collisions is higher than that at $\sqrt{s_{NN}}$ = 17.3 GeV and increases from peripheral to central collisions. These measurements indicate that the lifetime of the hot, dense medium created in central Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV is longer than those in peripheral collisions and at lower energies.
Reconstructed dielectron unlike-sign pairs, like-sign pairs and signal distributions, together with the signal to background ratio (S/B). All columns are presented as a function of dielectron invariant mass in Au+Au collisions at $\sqrt{s_{NN}}$ = 19.6 GeV.
Dielectron invariant mass spectrum in the STAR acceptance (|$y_{ee}$| < 1, 0.2 < $p_T^e$ < 3 GeV/c, |$\eta^e$ | < 1) after efficiency correction in Au+Au collisions at $\sqrt{s_{NN}}$ = 19.6 GeV.
Hadronic cocktail consisting of the decays of light hadrons and correlated decays of charm in Au+Au collisions at $\sqrt{s_{NN}}$ = 19.6 GeV.
The ratio of the yields of antiprotons to protons in pp collisions has been measured by the ALICE experiment at $\sqrt{s} = 0.9$ and $7$ TeV during the initial running periods of the Large Hadron Collider(LHC). The measurement covers the transverse momentum interval $0.45 < p_{\rm{t}} < 1.05$ GeV/$c$ and rapidity $|y| < 0.5$. The ratio is measured to be $R_{|y| < 0.5} = 0.957 \pm 0.006 (stat.) \pm 0.014 (syst.)$ at $0.9$ TeV and $R_{|y| < 0.5} = 0.991 \pm 0.005 (stat.) \pm 0.014 (syst.)$ at $7$ TeV and it is independent of both rapidity and transverse momentum. The results are consistent with the conventional model of baryon-number transport and set stringent limits on any additional contributions to baryon-number transfer over very large rapidity intervals in pp collisions.
The PT dependence of the pbar/p ratio for the central rapidity region ABS(YRAP)<0.5.
The central rapidity pbar/p ratio as a function of the rapidity interval Ybeam-Ybaryon and centre-of-mass energy. As well as the present ALICE measurements this table also lists the values from other experiments (see the text of the paper for details).
A study of the inclusive charged hadron production in two-photon collisions is described. The data were collected with the DELPHI detector at LEP II. Results on the inclusive single-particle p_T distribution and the differential charged hadrons dsigma/dp_T cross-section are presented and compared to the predictions of perturbative NLO QCD calculations and to published results.
Differential inclusive DSIG/DPT distribution of charged particles produced in GAMMA* GAMMA* interaction with two pseudorapidity cut offs.
The dissociation of virtual photons, $\gamma^{\star} p \to X p$, in events with a large rapidity gap between $X$ and the outgoing proton, as well as in events in which the leading proton was directly measured, has been studied with the ZEUS detector at HERA. The data cover photon virtualities $Q^2>2$ GeV$^2$ and $\gamma^{\star} p$ centre-of-mass energies $40<W<240$ GeV, with $M_X>2$ GeV, where $M_X$ is the mass of the hadronic final state, $X$. Leading protons were detected in the ZEUS leading proton spectrometer. The cross section is presented as a function of $t$, the squared four-momentum transfer at the proton vertex and $\Phi$, the azimuthal angle between the positron scattering plane and the proton scattering plane. It is also shown as a function of $Q^2$ and $\xpom$, the fraction of the proton's momentum carried by the diffractive exchange, as well as $\beta$, the Bjorken variable defined with respect to the diffractive exchange.
The differential cross section DSIG/DT for the LRG and the LPS data samples.
The fitted exponential slope of the T distribution as a function of X(NAME=POMERON).
The fitted exponential slope of the T distribution as a function of X(NAME=POMERON).
From a total data sample of 701.1 pb^-1 recorded with e+e- centre-of-mass energies of sqrt = 161-209 GeV with the OPAL detector at LEP, 11693 W-pair candidate events are selected. These data are used to obtain measurements of the W-pair production cross sections at 10 different centre-of-mass energies. The ratio of the measured cross sections to the Standard Model expectation is found to be: data/SM = 1.002 +- 0.011(stat.) +- 0.007(syst.) +- 0.005(theory), where the uncertainties are statistical, experimental systematics and theory systematics respectively. The data are used to determine the W boson branching fractions, which are found to be consistent with lepton universality of the charged current interaction. Assuming lepton universality, the branching ratio to hadrons is determined to be 67.41 +- 0.37(stat.) +- 0.23(syst.)%, from which the CKM matrix element Vcs is determined to be 0.96+-0.017(stat.)+-0.012(syst.). The differential cross section as a function of the W^- production angle is measured for the qqev and qqmv final states. The results described in this paper are consistent with the expectations from the Standard Model.
Measured cross section for the (lepton nu lepton nu) decay mode.
Measured cross section for the (quark quark lepton nu) decay mode.
Measured cross section for the (quark quark quark quark) decay mode.
Inclusive non-diffractive photoproduction of rho(770)^0, K^*(892)^0 and phi(1020) mesons is investigated with the H1 detector in ep collisions at HERA. The corresponding average \gamma p centre-of-mass energy is 210 GeV. The mesons are measured in the transverse momentum range 0.5<p_T<7 GeV and the rapidity range |y_{lab}|<1. Differential cross sections are presented as a function of transverse momentum and rapidity, and are compared to the predictions of hadroproduction models.
Inclusive non-diffractive photoproduction cross sections in the specified kinematic region.
Ratios of cross sections.
Inclusive non-diffractive photoproduction invariant differential cross sections as a function of PT in the specified kinematic range.
Forum