Charged particle multiplicity distributions in positron-proton deep inelastic scattering at a centre-of-mass energy $\sqrt{s}=319$ GeV are measured. The data are collected with the H1 detector at HERA corresponding to an integrated luminosity of $136$ pb${}^{-1}$. Charged particle multiplicities are measured as a function of photon virtuality $Q^2$, inelasticity $y$ and pseudorapidity $\eta$ in the laboratory and the hadronic centre-of-mass frames. Predictions from different Monte Carlo models are compared to the data. The first and second moments of the multiplicity distributions are determined and the KNO scaling behaviour is investigated. The multiplicity distributions as a function of $Q^2$ and the Bjorken variable $x_{\rm Bj}$ are converted to the hadron entropy $S_{\rm hadron}$, and predictions from a quantum entanglement model are tested.
Charged particle multiplicity distribution $P(N)$ measured as a function of the number of charged particles $N$ in 4x4 kinematic bins of $Q^2$ and $y$.
Charged particle multiplicity distribution $P(N)$ measured as a function of the number of charged particles $N$ in three overlapping pseudorapidity ranges $-1.2<\eta_{lab}\vert<0.2$, $-0.5<\eta_{lab}\vert<0.9$ and $0.2<\eta_{lab}\vert<1.6$, subdivided into 4x4 kinematic bins of $Q^2$ and $y$.
Charged particle multiplicity distribution $P(N)$ measured as a function of the number of charged particles $N$ with the additional restriction to select only particles from the current region of the Breit frame $0<\eta^{*}<4$, in 4x4 kinematic bins of $Q^2$ and $y$.
A semi-inclusive measurement of charged hadron multiplicities in deep inelastic muon scattering off an isoscalar target was performed using data collected by the COMPASS Collaboration at CERN. The following kinematic domain is covered by the data: photon virtuality $Q^{2}>1$ (GeV/$c$)$^2$, invariant mass of the hadronic system $W > 5$ GeV/$c^2$, Bjorken scaling variable in the range $0.003 < x < 0.4$, fraction of the virtual photon energy carried by the hadron in the range $0.2 < z < 0.8$, square of the hadron transverse momentum with respect to the virtual photon direction in the range 0.02 (GeV/$c)^2 < P_{\rm{hT}}^{2} < 3$ (GeV/$c$)$^2$. The multiplicities are presented as a function of $P_{\rm{hT}}^{2}$ in three-dimensional bins of $x$, $Q^2$, $z$ and compared to previous semi-inclusive measurements. We explore the small-$P_{\rm{hT}}^{2}$ region, i.e. $P_{\rm{hT}}^{2} < 1$ (GeV/$c$)$^2$, where hadron transverse momenta are expected to arise from non-perturbative effects, and also the domain of larger $P_{\rm{hT}}^{2}$, where contributions from higher-order perturbative QCD are expected to dominate. The multiplicities are fitted using a single-exponential function at small $P_{\rm{hT}}^{2}$ to study the dependence of the average transverse momentum $\langle P_{\rm{hT}}^{2}\rangle$ on $x$, $Q^2$ and $z$. The power-law behaviour of the multiplicities at large $P_{\rm{hT}}^{2}$ is investigated using various functional forms. The fits describe the data reasonably well over the full measured range.
Precise measurements of charged-kaon multiplicities in deep inelastic scattering were performed. The results are presented in three-dimensional bins of the Bjorken scaling variable x, the relative virtual-photon energy y, and the fraction z of the virtual-photon energy carried by the produced hadron. The data were obtained by the COMPASS Collaboration by scattering 160 GeV muons off an isoscalar 6 LiD target. They cover the kinematic domain 1 (GeV/c)2 < Q2 < 60 (GeV/c)^2 in the photon virtuality, 0.004 < x < 0.4, 0.1 < y < 0.7, 0.20 < z < 0.85, and W > 5 GeV/c^2 in the invariant mass of the hadronic system. The results from the sum of the z-integrated K+ and K- multiplicities at high x point to a value of the non-strange quark fragmentation function larger than obtained by the earlier DSS fit.
Multiplicities of positively charged kaons from semi-inclusive deep-inelastic scattering of muons off an isoscalar target, $M^{K^{+}}$, in bins of $x$, $y$, and $z$. Also given are the diffractive vector meson correction to the kaon count, $DVM^{K^{+}}$, and DIS count, $DVM^{DIS}$, as well as the radiative correction factors to the kaon count, $\eta^{K^{+}}$, and DIS count, $\eta^{DIS}$. The correction factors were applied to the raw multiplicity to arrive at the final multiplicity given in the table, $M^{K^{+}}$, as follows: $M^{K^{+}}$ = $M_{raw}^{K^{+}}$ * $\frac{\eta^{K^{+}}} {\eta^{DIS}}$ * $\frac{ DVM^{K^{+}} } {DVM^{DIS} }$.
Multiplicities of negatively charged kaons from semi-inclusive deep-inelastic scattering of muons off an isoscalar target, $M^{K^{-}}$, in bins of $x$, $y$, and $z$. Also given are the diffractive vector meson correction to the kaon count, $DVM^{K^{-}}$, and DIS count, $DVM^{DIS}$, as well as the radiative correction factors to the kaon count, $\eta^{K^{-}}$, and DIS count, $\eta^{DIS}$. The correction factors were applied to the raw multiplicity to arrive at the final multiplicity given in the table, $M^{K^{-}}$, as follows: $M^{K^{-}}$ = $M_{raw}^{K^{-}}$ * $\frac{\eta^{K^{-}}} {\eta^{DIS}}$ * $\frac{ DVM^{K^{-}} } {DVM^{DIS} }$.
Multiplicities of charged pions and unidentified hadrons produced in deep-inelastic scattering were measured in bins of the Bjorken scaling variable $x$, the relative virtual-photon energy $y$ and the relative hadron energy $z$. Data were obtained by the COMPASS Collaboration using a 160 GeV muon beam and an isoscalar target ($^6$LiD). They cover the kinematic domain in the photon virtuality $Q^2$ > 1(GeV/c$)^2$, $0.004 < x < 0.4$, $0.2 < z < 0.85$ and $0.1 < y < 0.7$. In addition, a leading-order pQCD analysis was performed using the pion multiplicity results to extract quark fragmentation functions.
Multiplicities of positively charged pions from semi-inclusive deep-inelastic scattering of muons off an isoscalar target, $M^{\pi^{+}}$, in bins of $x$, $y$, and $z$. Also given are the diffractive vector meson correction to the pion count, $DVM^{\pi^{+}}$, and DIS count, $DVM^{DIS}$, as well as the radiative correction factors to the pion count, $\eta^{\pi^{+}}$, and DIS count, $\eta^{DIS}$. The correction factors were applied to the raw multiplicity to arrive at the final multiplicity given in the table, $M^{\pi^{+}}$, as follows: $M^{\pi^{+}}$ = $M_{raw}^{\pi^{+}}$ * $\frac{\eta^{\pi^{+}}} {\eta^{DIS}}$ * $\frac{ DVM^{\pi^{+}} } {DVM^{DIS} }$.
Multiplicities of negatively charged pions from semi-inclusive deep-inelastic scattering of muons off an isoscalar target, $M^{\pi^{-}}$, in bins of $x$, $y$, and $z$. Also given are the diffractive vector meson correction to the pion count, $DVM^{\pi^{-}}$, and DIS count, $DVM^{DIS}$, as well as the radiative correction factors to the pion count, $\eta^{\pi^{-}}$, and DIS count, $\eta^{DIS}$. The correction factors were applied to the raw multiplicity to arrive at the final multiplicity given in the table, $M^{\pi^{-}}$, as follows: $M^{\pi^{-}}$ = $M_{raw}^{\pi^{-}}$ * $\frac{\eta^{\pi^{-}}} {\eta^{DIS}}$ * $\frac{ DVM^{\pi^{-}} } {DVM^{DIS} }$.
Multiplicities of unidentified positively charged hadrons from semi-inclusive deep-inelastic scattering of muons off an isoscalar target, $M^{h^{+}}$, in bins of $x$, $y$, and $z$. Also given are the diffractive vector meson correction to the hadron count, $DVM^{h^{+}}$, and DIS count, $DVM^{DIS}$, as well as the radiative correction factors to the hadron count, $\eta^{h^{+}}$, and DIS count, $\eta^{DIS}$. The correction factors were applied to the raw multiplicity to arrive at the final multiplicity given in the table, $M^{h^{+}}$, as follows: $M^{h^{+}}$ = $M_{raw}^{h^{+}}$ * $\frac{\eta^{h^{+}}} {\eta^{DIS}}$ * $\frac{ DVM^{h^{+}} } {DVM^{DIS} }$.
Multiplicities of charged hadrons produced in deep inelastic muon scattering off a $^6$LiD target have been measured as a function of the DIS variables $x_{Bj}$, $Q^2$, $W^2$ and the final state hadron variables $p_T$ and $z$. The $p_T^2$ distributions are fitted with a single exponential function at low values of $p_T^2$ to determine the dependence of $\langle p_T^2 \rangle$ on $x_{Bj}$, $Q^2$, $W^2$ and $z$. The $z$-dependence of $\langle p_T^2 \rangle$ is shown to be a potential tool to extract the average intrinsic transverse momentum squared of partons, $\langle k_{\perp}^2 \rangle$, as a function of $x_{Bj}$ and $Q^2$ in a leading order QCD parton model.
PT dependences of the differential multiplicities for 0.0045 < x_Bjorken < 0.0060 and 1.00 < Q^2 < 1.25 GeV^2 for Positive hadrons.
PT dependences of the differential multiplicities for 0.0060 < x_Bjorken < 0.0080 and 1.00 < Q^2 < 1.30 GeV^2 for Positive hadrons.
PT dependences of the differential multiplicities for 0.0060 < x_Bjorken < 0.0080 and 1.30 < Q^2 < 1.70 GeV^2 for Positive hadrons.
We present a comprehensive analysis of inclusive W(\to e\nu)+n-jet (n\geq 1,2,3,4) production in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV at the Tevatron collider using a 3.7 fb^{-1} dataset collected by the D0 detector. Differential cross sections are presented as a function of the jet rapidities (y), lepton transverse momentum (p_T) and pseudorapidity (\eta), the scalar sum of the transverse energies of the W boson and all jets (H_T), leading dijet p_T and invariant mass, dijet rapidity separations for a variety of jet pairings for p_T-ordered and angular-ordered jets, dijet opening angle, dijet azimuthal angular separations for p_T-ordered and angular-ordered jets, and W boson transverse momentum. The mean number of jets in an event containing a W boson is measured as a function of H_T, and as a function of the rapidity separations between the two highest-p_T jets and between the most widely separated jets in rapidity. Finally, the probability for third-jet emission in events containing a W boson and at least two jets is studied by measuring the fraction of events in the inclusive W+2-jet sample that contain a third jet over a p_T threshold. The analysis employs a regularized singular value decomposition technique to accurately correct for detector effects and for the presence of backgrounds. The corrected data are compared to particle level next-to-leading order perturbative QCD predictions, predictions from all-order resummation approaches, and a variety of leading-order and matrix-element plus parton-shower event generators. Regions of the phase space where there is agreement or disagreement with the data are discussed for the different models tested.
Differential production cross-section, normalized to the measured inclusive W boson cross-section, as a function of leading jet rapidity for events with one or more jets produced in association with a W boson. First uncertainty is statistical, second uncertainty is systematic.
Differential production cross-section, normalized to the measured inclusive W boson cross-section, as a function of second jet rapidity for events with two or more jets produced in association with a W boson. First uncertainty is statistical, second uncertainty is systematic.
Differential production cross-section, normalized to the measured inclusive W boson cross-section, as a function of third jet rapidity for events with three or more jets produced in association with a W boson. First uncertainty is statistical, second uncertainty is systematic.
The charged particle production in proton-proton collisions is studied with the LHCb detector at a centre-of-mass energy of ${\sqrt{s} =7}$TeV in different intervals of pseudorapidity $\eta$. The charged particles are reconstructed close to the interaction region in the vertex detector, which provides high reconstruction efficiency in the $\eta$ ranges $-2.5<\eta<-2.0$ and $2.0<\eta<4.5$. The data were taken with a minimum bias trigger, only requiring one or more reconstructed tracks in the vertex detector. By selecting an event sample with at least one track with a transverse momentum greater than 1 GeV/c a hard QCD subsample is investigated. Several event generators are compared with the data; none are able to describe fully the multiplicity distributions or the charged particle density distribution as a function of $\eta$. In general, the models underestimate the charged particle production.
Charged particle multiplicity distribution in minimum bias events for different pseudorapidity bins. The first quoted uncertainty is statistical and the second is systematic.
Charged particle multiplicity distribution in hard QCD events for different pseudorapidity bins. The first quoted uncertainty is statistical and the second is systematic.
Charged particle multiplicity distribution for minimum bias events in the full pseudorapidity range. The first quoted uncertainty is statistical and the second is systematic.
We report the first measurements of the kurtosis (\kappa), skewness (S) and variance (\sigma^2) of net-proton multiplicity (N_p - N_pbar) distributions at midrapidity for Au+Au collisions at \sqrt(s_NN) = 19.6, 62.4, and 200 GeV corresponding to baryon chemical potentials (\mu_B) between 200 - 20 MeV. Our measurements of the products \kappa \sigma^2 and S \sigma, which can be related to theoretical calculations sensitive to baryon number susceptibilities and long range correlations, are constant as functions of collision centrality. We compare these products with results from lattice QCD and various models without a critical point and study the \sqrt(s_NN) dependence of \kappa \sigma^2. From the measurements at the three beam energies, we find no evidence for a critical point in the QCD phase diagram for \mu_B below 200 MeV.
$\Delta N_p$ multiplicity distribution in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV for 0-5 percent central collisions at midrapidity (| y |< 0.5).
$\Delta N_p$ multiplicity distribution in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV for 30-40 percent central collisions at midrapidity (| y |< 0.5).
$\Delta N_p$ multiplicity distribution in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV for 70-80 percent central collisions at midrapidity (| y |< 0.5).
We present the multiplicity and pseudorapidity distributions of photons produced in Au+Au and Cu+Cu collisions at \sqrt{s_NN} = 62.4 and 200 GeV. The photons are measured in the region -3.7 < \eta < -2.3 using the photon multiplicity detector in the STAR experiment at RHIC. The number of photons produced per average number of participating nucleon pairs increases with the beam energy and is independent of the collision centrality. For collisions with similar average numbers of participating nucleons the photon multiplicities are observed to be similar for Au+Au and Cu+Cu collisions at a given beam energy. The ratios of the number of charged particles to photons in the measured pseudorapidity range are found to be 1.4 +/- 0.1 and 1.2 +/- 0.1 for \sqrt{s_NN} = 62.4 GeV and 200 GeV, respectively. The energy dependence of this ratio could reflect varying contributions from baryons to charged particles, while mesons are the dominant contributors to photon production in the given kinematic region. The photon pseudorapidity distributions normalized by average number of participating nucleon pairs, when plotted as a function of \eta - ybeam, are found to follow a longitudinal scaling independent of centrality and colliding ion species at both beam energies.
Fig. 1. (Color online.) Top panel: Photon reconstruction efficiency $\left(\epsilon_{\gamma}\right)$ (solid symbols) and purity of photon sample $\left(f_{\mathrm{p}}\right)$ (open symbols) for PMD as a function of pseudorapidity $(\eta)$ for minimum bias $\mathrm{Au}+\mathrm{Au}$ and $\mathrm{Cu}+\mathrm{Cu}$ at $\sqrt{s_{\mathrm{NN}}}=$ $200 \mathrm{GeV}$. Bottom panel: Comparison between estimated $\epsilon_{\gamma}$ and $f_{\mathrm{p}}$ for PMD as a function of $\eta$ for minimum bias $\mathrm{Au}+\mathrm{Au}$ at $\sqrt{s_{\mathrm{NN}}}=62.4 \mathrm{GeV}$ using HIJING and AMPT models. The error bars on the AMPT data are statistical and those for HIJING are within the symbol size. NOTE: For points with invisible error bars, the point size was considered as an absolute upper limit for the uncertainty.
Fig. 1. (Color online.) Top panel: Photon reconstruction efficiency $\left(\epsilon_{\gamma}\right)$ (solid symbols) and purity of photon sample $\left(f_{\mathrm{p}}\right)$ (open symbols) for PMD as a function of pseudorapidity $(\eta)$ for minimum bias $\mathrm{Au}+\mathrm{Au}$ and $\mathrm{Cu}+\mathrm{Cu}$ at $\sqrt{s_{\mathrm{NN}}}=$ $200 \mathrm{GeV}$. Bottom panel: Comparison between estimated $\epsilon_{\gamma}$ and $f_{\mathrm{p}}$ for PMD as a function of $\eta$ for minimum bias $\mathrm{Au}+\mathrm{Au}$ at $\sqrt{s_{\mathrm{NN}}}=62.4 \mathrm{GeV}$ using HIJING and AMPT models. The error bars on the AMPT data are statistical and those for HIJING are within the symbol size. NOTE: For points with invisible error bars, the point size was considered as an absolute upper limit for the uncertainty.
Fig. 2. (Color online.) Event-by-event photon multiplicity distributions (solid circles) for $\mathrm{Au}+\mathrm{Au}$ and $\mathrm{Cu}+\mathrm{Cu}$ at $\sqrt{s_{\mathrm{NN}}}=62.4$ and $200 \mathrm{GeV} .$ The distributions for top $0-5 \%$ central $\mathrm{Au}+$ Au collisions and top $0-10 \%$ central $\mathrm{Cu}+\mathrm{Cu}$ collisions are also shown (open circles). The photon multiplicity distributions for central collisions are observed to be Gaussian (solid line). Only statistical errors are shown. NOTE: For points with invisible error bars, the point size was considered as an absolute upper limit for the uncertainty.
The average charged track multiplicity and the normalised distribution of the scaled momentum, $\xp$, of charged final state hadrons are measured in deep-inelastic $\ep$ scattering at high $Q^2$ in the Breit frame of reference. The analysis covers the range of photon virtuality $100 < Q^2 < 20 000 \GeV^{2}$. Compared with previous results presented by HERA experiments this analysis has a significantly higher statistical precision and extends the phase space to higher $Q^{2}$ and to the full range of $\xp$. The results are compared with $e^+e^-$ annihilation data and with various calculations based on perturbative QCD using different models of the hadronisation process.
Average values of Q and X (plus errors) for the different Q**2 ranges.
Average charged hadron multiplicity as a function of Q**2.
Normalised distribution of the scaled momentum as a function of Q**2 in the X range 0 to 0.02.
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