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: $M^{K^{-}}$ = $M_{raw}^{K^{-}}$ * $\frac{\eta^{K^{-}}} {\eta^{DIS}}$ * $\frac{ DVM^{K^{-}} } {DVM^{DIS} }$.
Measurements of distributions of charged particles produced in proton-proton collisions with a centre-of-mass energy of 13 TeV are presented. The data were recorded by the ATLAS detector at the LHC and correspond to an integrated luminosity of 151 $\mu$b$^{-1}$. The particles are required to have a transverse momentum greater than 100 MeV and an absolute pseudorapidity less than 2.5. The charged-particle multiplicity, its dependence on transverse momentum and pseudorapidity and the dependence of the mean transverse momentum on multiplicity are measured in events containing at least two charged particles satisfying the above kinematic criteria. The results are corrected for detector effects and compared to the predictions from several Monte Carlo event generators.
The average charged-particle muliplicity per unit of rapidity for ETARAP=0 as a function of the centre-of-mass energy.
The average charged-particle muliplicity per unit of rapidity for ETARAP=0 as a function of the centre-of-mass energy.
The extrapolated ($\tau > 30$ ps) average charged-particle muliplicity per unit of rapidity for ETARAP=0 as a function of the centre-of-mass energy.
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: $M^{h^{+}}$ = $M_{raw}^{h^{+}}$ * $\frac{\eta^{h^{+}}} {\eta^{DIS}}$ * $\frac{ DVM^{h^{+}} } {DVM^{DIS} }$.
This paper presents measurements of distributions of charged particles which are produced in proton--proton collisions at a centre-of-mass energy of $\sqrt{s} = 8$ TeV and recorded by the ATLAS detector at the LHC. A special dataset recorded in 2012 with a small number of interactions per beam crossing (below 0.004) and corresponding to an integrated luminosity of $160 \mathrm{\mu b^{-1}}$ was used. A minimum-bias trigger was utilised to select a data sample of more than 9 million collision events. The multiplicity, pseudorapidity, and transverse momentum distributions of charged particles are shown in different regions of kinematics and charged-particle multiplicity, including measurements of final states at high multiplicity. The results are corrected for detector effects and are compared to the predictions of various Monte Carlo event generator models which simulate the full hadronic final state.
Central primary-charged-particle density 1/Nev dNch/deta at eta = 0 for five different phase spaces. The results are given for the fiducial definition tau > 300 ps, as well as for the previously used fiducial definition tau > 30 ps using an extrapolation factor of 1.012 +- 0.004 (for pT > 100 MeV) or 1.025 +- 0.008 (for pT > 500 MeV), which accounts for the fraction of charged strange baryons predicted by Epos LHC simulation.
Charged-particle multiplicity distributions in proton-proton collisions at a centre-of mass energy of 8000 GeV for events with the number of charged particles >=2 having transverse momentum >100 MeV and absolute(pseudorapidity) <2.5.
Charged-particle multiplicity distributions in proton-proton collisions at a centre-of mass energy of 8000 GeV for events with the number of charged particles >=1 having transverse momentum >500 MeV and absolute(pseudorapidity) <2.5.
Charged-particle distributions are measured in proton-proton collisions at a centre-of-mass energy of 13 TeV, using a data sample of nearly 9 million events, corresponding to an integrated luminosity of 170 $\mu$b$^{-1}$, recorded by the ATLAS detector during a special Large Hadron Collider fill. The charged-particle multiplicity, its dependence on transverse momentum and pseudorapidity and the dependence of the mean transverse momentum on the charged-particle multiplicity are presented. The measurements are performed with charged particles with transverse momentum greater than 500 MeV and absolute pseudorapidity less than 2.5, in events with at least one charged particle satisfying these kinematic requirements. Additional measurements in a reduced phase space with absolute pseudorapidity less than 0.8 are also presented, in order to compare with other experiments. The results are corrected for detector effects, presented as particle-level distributions and are compared to the predictions of various Monte Carlo event generators.
The average charged-particle multiplicity per unit of rapidity for ETARAP=0 as a function of the centre-of-mass energy.
The extrapolated average charged-particle multiplicity per unit of rapidity for ETARAP=0 as a function of the centre-of-mass energy.
Charged-particle multiplicities in proton-proton collisions at a centre-of-mass energy of 13000 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 c .m.s. angular distributions of protons and 1r mesons emitted in emulsions in protonproton collisions were measured. The proton angular distribution is symmetric and possesses a pronounced anisotropy. The n-meson distribution is symmetric and more isotropic. The angular dependence of the total energy in the c .m .s. has been determined for protons. It is shown that, on the average, protons expend about 74% of their energy in the c.m.s. on meson production. Within the limits of experimental error, the mean values of the transverse momentum and the total energy in the c .m.s. are the same for various multiplicities.
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This investigation was performed with a 24-liter propane bubble chamber [i] and is a continu- ation of our previous work on the production of strange particles by 7-8-BeV 1r- mesons on hydrogen and carbon. [ 2 - 5 ] The properties of 1r 0 mesons inferred from the y quanta accom- panying A and K 0 production are given, and are compared with the properties of 1r+ and 7r- mesons emitted in A and K 0 production processes. The possibility of a resonance with radi- ative decay is noted.
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We have investigated the particle production and fragmentation of nuclei participating in the interactions of 10.6 GeV/n gold nuclei in nuclear emulsions. A new criterion has been found to distinguish between the interactions of these gold nuclei with the light (H,C,N,O) and heavy (Ag, Br) target nuclei in the emulsion. This has allowed separate analyses of the multiplicity and pseudo-rapidity distributions of the singly charged particles emitted in Au-(H,C,N,O) and Au-(Ag,Br) interactions, as well as of the modes of breakup of the projectile and target nuclei. The pseudo-rapidity distributions show strong forward asymmetries, particularly for the interactions with the light nuclei. Heavy target nuclei produce a more severe breakup of the projectile gold nucleus than do the lighter targets. A negative correlation between the number of fragments emitted from the target nuclei and the degree of centrality of the collisions has been observed, which can be attributed to the total destruction of the relatively light target nuclei by these very heavy projectile nuclei.
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Measurements of fiducial cross sections for the electroweak production of two jets in association with a Z-boson are presented. The measurements are performed using 20.3 inverse femtobarns of proton-proton collision data collected at a centre-of-mass energy of sqrt(s)=8 TeV by the ATLAS experiment at the Large Hadron Collider. The electroweak component is extracted by a fit to the dijet invariant mass distribution in a fiducial region chosen to enhance the electroweak contribution over the dominant background in which the jets are produced via the strong interaction. The electroweak cross sections measured in two fiducial regions are in good agreement with the Standard Model expectations and the background-only hypothesis is rejected with significance above the 5 sigma level. The electroweak process includes the vector boson fusion production of a Z-boson and the data are used to place limits on anomalous triple gauge boson couplings. In addition, measurements of cross sections and differential distributions for inclusive Z-boson-plus-dijet production are performed in five fiducial regions, each with different sensitivity to the electroweak contribution. The results are corrected for detector effects and compared to predictions from the SHERPA and POWHEG event generators.
Unfolded normalised differential Z+2j cross section as a function of dijet invariant mass in the baseline region.
Unfolded normalised differential Z+2j cross section as a function of dijet invariant mass in the search region.
Unfolded normalised differential Z+2j cross section as a function of the rapidity separation between the leading jets in the baseline region.
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