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+>.
Measurements of multiplicity and transverse momentum fluctuations of charged particles were performed in inelastic p+p interactions at 20, 31, 40, 80 and 158 GeV/c beam momentum. Results for the scaled variance of the multiplicity distribution and for three strongly intensive measures of multiplicity and transverse momentum fluctuations \$\Delta[P_{T},N]\$, \$\Sigma[P_{T},N]\$ and \$\Phi_{p_T}\$ are presented. For the first time the results on fluctuations are fully corrected for experimental biases. The results on multiplicity and transverse momentum fluctuations significantly deviate from expectations for the independent particle production. They also depend on charges of selected hadrons. The string-resonance Monte Carlo models EPOS and UrQMD do not describe the data. The scaled variance of multiplicity fluctuations is significantly higher in inelastic p+p interactions than in central Pb+Pb collisions measured by NA49 at the same energy per nucleon. This is in qualitative disagreement with the predictions of the Wounded Nucleon Model. Within the statistical framework the enhanced multiplicity fluctuations in inelastic p+p interactions can be interpreted as due to event-by-event fluctuations of the fireball energy and/or volume.
Energy dependence of $\Delta[P_{T},N]$ for three charge selections
Energy dependence of $\Delta[P_{T},N]$ for three charge selections
Energy dependence of $\Sigma[P_{T},N]$ for three chrge selections
Measurements of inclusive spectra and mean multiplicities of $\pi^\pm$, K$^\pm$, p and $\bar{\textrm{p}}$ produced in inelastic p+p interactions at incident projectile momenta of 20, 31, 40, 80 and 158 GeV/c ($\sqrt{s} = $ 6.3, 7.7, 8.8, 12.3 and 17.3 GeV, respectively) were performed at the CERN Super Proton Synchrotron using the large acceptance NA61/SHINE hadron spectrometer. Spectra are presented as function of rapidity and transverse momentum and are compared to predictions of current models. The measurements serve as the baseline in the NA61/SHINE study of the properties of the onset of deconfinement and search for the critical point of strongly interacting matter.
Transverse momentum-rapidity spectrum of K− produced in inelastic p+p interactions at 31 GeV/c with statistical uncertainties.
Transverse momentum-rapidity spectrum of K− produced in inelastic p+p interactions at 20 GeV/c with systematic uncertainties.
Transverse momentum-rapidity spectrum of K+ produced in inelastic p+p interactions at 20 GeV/c with statistical uncertainties.
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We present experimental results on inclusive spectra and mean multiplicities of negatively charged pions produced in inelastic p+p interactions at incident projectile momenta of 20, 31, 40, 80 and 158 GeV/c ($\sqrt{s} = $ 6.3, 7.7, 8.8, 12.3 and 17.3 GeV, respectively). The measurements were performed using the large acceptance NA61/SHINE hadron spectrometer at the CERN Super Proton Synchrotron. Two-dimensional spectra are determined in terms of rapidity and transverse momentum. Their properties such as the width of rapidity distributions and the inverse slope parameter of transverse mass spectra are extracted and their collision energy dependences are presented. The results on inelastic p+p interactions are compared with the corresponding data on central Pb+Pb collisions measured by the NA49 experiment at the CERN SPS. The results presented in this paper are part of the NA61/SHINE ion program devoted to the study of the properties of the onset of deconfinement and search for the critical point of strongly interacting matter. They are required for interpretation of results on nucleus-nucleus and proton-nucleus collisions.
Transverse momentum spectra of $\pi^-$ mesons produced in inelastic $p p$ interactions at 20 GeV in various rapidity ranges.
Transverse momentum spectra of $\pi^-$ mesons produced in inelastic $p p$ interactions at 20 GeV in various rapidity ranges.
Transverse momentum spectra of $\pi^-$ mesons produced in inelastic $p p$ interactions at 20 GeV in various rapidity ranges.
Phi meson production is studied by the NA49 collaboration in central Pb+Pb collisions at 20A, 30A, 40A, 80A and 158A GeV beam energy. The data are compared to measurements at lower and higher energies and to microscopic and thermal models. The energy dependence of yields and spectral distributions is compatible with the assumption that partonic degrees of freedom set in at low SPS energies.
PHI transverse momentum spectra at incident energy 20 GeV/nucleon integrated over the rapidity range 0 to 1.8.
PHI transverse momentum spectra at incident energy 30 GeV/nucleon integrated over the rapidity range 0 to 1.8.
PHI transverse momentum spectra at incident energy 40 GeV/nucleon integrated over the rapidity range 0 to 1.5.
Results on charged pion and kaon production in central Pb+Pb collisions at 20A and 30A GeV are presented and compared to data at lower and higher energies. A rapid change of the energy dependence is observed around 30A GeV for the yields of pions and kaons as well as for the shape of the transverse mass spectra. The change is compatible with the prediction that the threshold for production of a state of deconfined matter at the early stage of the collisions is located at low SPS energies.
Transverse mass spectra for pion production in the central rapidity region for collisions at 20 GeV per nucleon.
Transverse mass spectra for pion production in the central rapidity region for collisions at 30 GeV per nucleon.
Transverse mass spectra for kaon production in the central rapidity region for collisions at 20 GeV per nucleon.
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NUCLEUS IS P, C, AL.
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The measurements of the differential cross section of elastic p-p scattering in relative units were performed in the energy range of 12–70 GeV. The values of the slope parameter were obtained from this data. It was shown that the slope parameter of the differential p-p scattering is monotonously increasing when the proton energy rises in the range 12–70 GeV. We have obtained the slope Pomeranchuk's pole trajectory from this data: α′ p = 0.40 ± 0.09.
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We present inclusive ¶ and K *0 (892) cross sections and Feynman x -spectra in K + p collisions at 250 GeV/ c . In the K + fragmentation region, x > 0.2, the ratio of ¶ to K *0 (892) is used to estimate the strangeness suppression factor λ , with the result γ =0.17 ± 0.02 (stat ± 0.01 (syst). We see no evidence for an energy dependence of λ in the CM energy range 7.8 ≤ s ≤21.7 GeV.
RESULTS AT 32 AND 70 GEV INCLUDED FOR COMPARISON.
RESULTS AT 32 AND 70 GEV INCLUDED FOR COMPARISON.
RESULTS AT 32 AND 70 GEV INCLUDED FOR COMPARISON.
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Energy, charge and strangeness flow inK+p interactions at 32 and 70 GeV/c, and π+p interactions at 32 GeV/c are studied in terms of the angular variable λ=|x|/pT. The data ondQ/dλ anddE/dλ show only a weak indication of scale breaking between 32 and 70 GeV/c. For inclusive “non-diffractive”, inclusive “diffractive” and exclusive “non-diffractive” jets, the fraction of charge in any angular region ΔΩ away from the central region is found to be proportional to the energy fraction in the same interval. The data ondQ/dE versus λ are compatible with some versions of dual-sheet models and agree also with the LUND Monte-Carlo model. The data are also compared with\(v(\bar v)p\) interactions in BEBC. In exclusive channels the average ratiodQ/dS=0.78±0.04 is consistent, in the framework of fragmentation models, with a larger probability for the fragmentation of the\(\bar s\)-valence quark than theu-valence quark in theK+-meson.
CHARGE FLOW IN NONDIFFRACTIVE PROTON-LIKE AND KAON-LIKE JETS.
CHARGE FLOW IN NONDIFFRACTIVE PROTON-LIKE AND KAON-LIKE JETS.
CHARGE FLOW IN NONDIFFRACTIVE PROTON-LIKE AND KAON-LIKE JETS.
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We present results on inclusive particle production in the antineutrino charged current induced hadron jets observed in the Fermilab 15 ft bubble chamber. Fractional energy distributions, particle ratios and average multiplicities of the hadrons in the jets are measured. Ratios between the inclusive production rates of different mesons in the jets are studied to seek evidence for the d-quark origin of the observed hadrons. Good over-all agreement with the hypothesis of d-quark fragmentation with universal fragmentation functions obeying isospin systematics is established.
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The differential cross-sections in the range of four momentum transfer squared from 0.003 to 0.120 (GeV c) 2 were measured at 30, 50 and 70 GeV by using a thin polyethilene target in the internal proton beam of the Serpukhov accelerator. The slope parameter, the ratio of the real to the imaginary part of the forward amplitude and the cross-section in the diffraction cone were measured.
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ASSUMING UNIFORM SLOPE.
We present results on the experimental study of inelastic charged-current antineutrino-nucleon scattering in the energy range of 10–200 GeV. The data sample, consisting of about 6500 antineutrino-induced events, was obtained in the Fermilab 15 ft bubble chamber filled with a heavy neon-hydrogen mixture. The differential cross sections for ν μ N interactions are presented in terms of scaling variables x and y . The structure functions F 2 ν and xF 3 ν have been evaluated as functions of x and E ν . A deviation from the scaling hypothesis, similar to those found in other experiments on inelastic lepton-nucleon scattering, has been observed. The data are interpreted in the framework of the quark-parton model. Quark and antiquark distributions and their energy dependences are presented.
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The first observation of μ + e + events produced in antineutrino interactions using the Fermilab 15 ft bubble chamber is reported. The relative yield of μ + e + events is (4.8 −3.2 +5.3 ) × 10 −4 of all charged-current events with antineutrino energy greater than 10 GeV. The observed V 0 rate is 1.0 −1.0 +1.2 per μ + e + event. Possible sources of these events are discussed.
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We have studied transverse momenta of charged hadrons in the current fragmentation region of charged current antineutrino- nucleon interactions observed in the Fermilab 15 ft bubble chamber. The measured momentum squared transverse to the v μ + plane (p out 2 ) of the negative hadrons varies as a function of Q 2 , W 2 and x as expected from t he leading order perturbative QCD calculations. Positively charged hadrons show a different transverse momentum behaviour as a function of Q 2 .
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The results of a study of strange particle production in charged current $\bar{\nu}_{\mu} N$ interactions in the Fermilab 15 ft bubble chamber filled with a heavy $Ne-H_2$ mixture are presented. Production rates and average multiplicities of $K^0$'s and Λ's as functions of W 2 and Q 2 are given. The experimental data agree well with the quark-parton model predictions if a yield of 0.06 ± 0.02 of $K^0$'s and Λ's from charm production is included. Upper limits for D-meson production are given and the shape of the charmed quark fragmentation function is discussed. Inclusive production of the K ∗ (890) and Σ(1385) resonances is measured and it is shown that only about 5% of the K 0 mesons and Λ hyperons results from resonance decays. Relative production rates of neutral strange particles on proton and neutron targets are studied.
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We have used the ratio between the production rates of $K^0$'s and $π^−$'s in antineutrino-nucleon interactions in the Fermilab 15 ft bubble chamber to measure the size of the SU (3) symmetry violation in the production of quark-antiquark pairs to be 0.27 ± 0.04. This value is significantly larger than the value obtained from a recent ep experiment. There is no apparent dependence of the $K^0$/$π^−$ ratio with $W^2 , Q ^2 , x_b$ or $p_T^2$ .
OBTAINED RESULT FOR SIG/SIG IS MODEL DEPENDENT.
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FOR -T = 0.002 TO 0.05 GEV**2.
In this paper we present tables of absolute differential cross sections of elastic pp scattering together with the values of the slope parameter B and the real-part parameter α, where B= d d t In dσ d t α= Re A(0) Im A(0) and A (0) is the amplitude of elastic pp scattering at t = 0. The cross-section data have been obtained at the Serpukhov accelerator from 8 to 70 GeV in the | t |-range 0.0007 − 0.12 (GeV/ c ) 2 .
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The total elastic p-p, p-d and p-n cross sections measured at the Serpukhov accelerator and Dubna synchrophasotron are presented in this paper.
SLOPE MEASURED FOR -T = 0.08 TO 0.12 GEV**2.
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Proton-proton elastic scattering has been measured over the four-momentum transfer squared 0.0007 ⩽ t ⩽ 0.02 GeV 2 /c 2 . A gas hydrogen jet has been used as an internal target of the accelerator. The results indicate that the ratio of the real to the imaginary part of the proton-proton forward scattering amplitude rises smoothly with increasing energy from α = −0.35 ± 0.05 at p = 9.39 GeV/ c to α = −0.092 ± 0.011 at p = 69.8 GeV/ c .
THE TOTAL ELASTIC CROSS SECTION IS DERIVED FROM THE OPTICAL THEOREM POINT AND SLOPE PARAMETER.
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