536 Search Results

Double-differential yields of $${\Xi \left( 1530\right) ^{0}} $$ and $${\overline{\Xi }\left( 1530\right) ^{0}} $$ resonances produced in p+p interactions were measured at a laboratory beam momentum of 158 $$\text{ GeV }\!/\!c$$. This measurement is the first of its kind in p+p interactions below LHC energies. It was performed at the CERN SPS by the NA61/SHINE collaboration. Double-differential distributions in rapidity and transverse momentum were obtained from a sample of $$26\times 10^6$$ inelastic events. The spectra are extrapolated to full phase space resulting in mean multiplicity of $${\Xi \left( 1530\right) ^{0}} $$ ($$6.73 \pm 0.25\pm 0.67)\times 10^{-4}$$ and $${\overline{\Xi }\left( 1530\right) ^{0}} $$more » ($$2.71 \pm 0.18\pm 0.18)\times 10^{-4}$$. The rapidity and transverse momentum spectra and mean multiplicities were compared to predictions of string-hadronic and statistical model calculations.« less

The physics goal of the strong interaction program of the NA61/SHINE experiment at the CERN Super Proton Synchrotron (SPS) is to study the phase diagram of hadronic matter by a scan of particle production in collisions of nuclei with various sizes at a set of energies covering the SPS energy range. This paper presents differential inclusive spectra of transverse momentum, transverse mass and rapidity of π^- mesons produced in central ⁴⁰Ar+⁴⁵Sc collisions at beam momenta of 13A, 19A, 30A, 40A, 75A and 150A Ge V /c. Energy and system size dependence of parameters of these distributions – mean transverse mass,more » the inverse slope parameter of transverse mass spectra, width of the rapidity distribution and mean multiplicity – are presented and discussed. Furthermore, the dependence of the ratio of the mean number of produced pions to the mean number of wounded nucleons on the collision energy was derived. The results are compared to predictions of several models.« less

Measurements of multiplicity fluctuations of identified hadrons produced in inelastic p+p interactions at 31, 40, 80, and 158 $$\text {Ge}\text {V}/c$$ beam momentum are presented. Three different measures of multiplicity fluctuations are used: the scaled variance $$\omega $$ and strongly intensive measures $$\Sigma $$ and $$\Delta $$. These fluctuation measures involve second and first moments of joint multiplicity distributions. Data analysis is preformed using the Identity method which corrects for incomplete particle identification. Strongly intensive quantities are calculated in order to allow for a direct comparison to corresponding results on nucleus–nucleus collisions. The results for different hadron types are shown asmore » a function of collision energy. A comparison with predictions of string-resonance Monte-Carlo models: Epos, Smash and Venus, is also presented.« less

The second-order Fourier coefficients ( $v_2$) characterizing the azimuthal distributions of Υ(1S) and Υ(2S) mesons produced in PbPb collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=5.02\text{TeV}$ are studied. The Υ mesons are reconstructed in their dimuon decay channel, as measured by the CMS detector. The collected data set corresponds to an integrated luminosity of $1.7{\text{nb}}^{-1}$. The scalar product method is used to extract the ${more »}_{}$ v 2 coefficients of the azimuthal distributions. Results are reported for the rapidity range $\left|y\right|<2.4$, in the transverse momentum interval $0<p_{\mathrm{T}}<50\text{GeV}/c$, and in three centrality ranges of 10–30%, 30–50% and 50–90%. In contrast to the $\mathrm{J}/\mathit{\psi }$ mesons, the measured $v_2$ values for the Image 5 mesons are found to be consistent with zero.« less

The NA61/SHINE experiment at the CERN Super Proton Synchrotron (SPS) studies the onset of deconfinement in hadron matter by a scan of particle production in collisions of nuclei with various sizes at a set of energies covering the SPS energy range. This paper presents results on inclusive double-differential spectra, transverse momentum and rapidity distributions and mean multiplicities of $$\pi^, \pm K^\pm$$ p and $$\bar{p}$$ produced in the 20% most central Be+$^9$ Be collisions at beam momenta of 19A, 30A, 40A, 75A and 150A $${\mathrm{Ge} \mathrm{V}}\!/\!c$$. The energy dependence of the $$K^\pm/ \pi^\pm$$ ratios as well as of inverse slope parameters ofmore » the $$K^\pm$$ transverse mass distributions are close to those found in inelastic $p+p$ reactions. The new results are compared to the world data on $p+p and Pb+Pb collisions as well as to predictions of the Epos, Urqmd, Ampt, Phsd and Smash models.« less

The production cross section of 30.92 GeV/c protons on carbon is measured by the NA61/SHINE spectrometer at the CERN Super Proton Synchrotron by means of beam attenuation in a copy (replica) of the 90-cm-long target of the T2K neutrino oscillation experiment. The employed method for direct production cross-section estimation minimizes model corrections for elastic and quasielastic interactions. The obtained production cross section is $$σ_{\text{prod}}$$ = 227.6 ± 0.8(stat)$$_{\text{-3.2}}^{\text{+1.9}}$$(sys) – 0.8(mod) mb. It is in agreement with previous NA61/SHINE results obtained with a thin carbon target, while providing improved precision with a total fractional uncertainty of less than 2%. This directmore » measurement will reduce the uncertainty of the T2K neutrino flux prediction.« less

A measurement of charged hadron pair correlations in two-dimensional $$\Delta \eta \Delta \phi $$ space is presented. The analysis is based on total 30 million central Be + Be collisions observed in the NA61/SHINE detector at the CERN SPS for incident beam momenta of 19A, 30A, 40A, 75A, and 150A $$\text {Ge} \text {V}/c$$. Measurements were carried out for unlike-sign and like-sign charge hadron pairs independently. The $$C(\Delta \eta ,\Delta \phi )$$ correlation functions were compared with results from a similar analysis on p + p interactions at similar beam momenta per nucleon. General trends of the back-to-back correlations are similar in central Be + Be collisionsmore » and p + p interactions, but are suppressed in magnitude due to the increased combinatorial background. Predictions from the Epos and UrQMD models are compared to the measurements. Evolution of an enhancement around $$(\Delta \eta ,\Delta \phi ) = (0,0)$$ with incident energy is observed in central Be + Be collisions. It is not predicted by both models and almost non-existing in proton–proton collisions at the same momentum per nucleon.« less

The NA61/SHINE collaboration studies at the CERN Super Proton Synchrotron (SPS) the onset of deconfinement in hadronic matter by the measurement of particle production in collisions of nuclei with various sizes at a set of energies covering the SPS energy range. This paper presents results on inclusive double-differential spectra and mean multiplicities of $$\pi^{-}$$ mesons produced in the 5% most central $^7$Be + $^9$Be collisions at beam momenta of 19$$A$$, 30$$A$$, 40$$A$$, 75$$A$$ and 150$$A$$ GeV/$$c$$ obtained by the so-called $h^-$ method which does not require any particle identification. The shape of the transverse mass spectra differs from the shapesmore » measured in central Pb + Pb collisions and inelastic p + p interactions. The normalized width of the rapidity distribution decreases with increasing collision energy and is in between the results for inelastic nucleon-nucleon and central Pb + Pb collisions. The mean multiplicity of pions per wounded nucleon in central $^7$Be + $^9$Be collisions is close to that in central Pb + Pb collisions up to 75$$A$$GeV/$$c$$. However, at the top SPS energy the result is close to the one for inelastic nucleon-nucleon interactions. The results are discussed in the context of predictions for the onset of deconfinement at the CERN SPS collision energies.« less

The production of $$\Xi (1321)^{-}$$ and $$\overline{\Xi }(1321)^{+}$$ hyperons in inelastic $p+p$ interactions is studied in a fixed target experiment at a beam momentum of 158 $$\hbox {Ge}\hbox {V}\!/\!c$$. Double differential distributions in rapidity $${y}$$ and transverse momentum $$p_{T}$$ are obtained from a sample of 33M inelastic events. They allow to extrapolate the spectra to full phase space and to determine the mean multiplicity of both $${\Xi }{^-}$$ and $$\overline{\Xi }{^+} $$. The rapidity and transverse momentum spectra are compared to transport model predictions. The $${\Xi }{^-} $$ mean multiplicity in inelastic $p+p$ interactions at 158 $$\hbox {Ge}\hbox {V}\!/\!c$$ is used tomore » quantify the strangeness enhancement in A+A collisions at the same centre-of-mass energy per nucleon pair.« less