Strangeness in nuclear collisions

Gazdzicki, Marek ; Rohrich, Dieter ;
Z.Phys.C 71 (1996) 55-64, 1996.
Inspire Record 420462 DOI 10.17182/hepdata.13638

Data on the mean multiplicity of strange hadrons produced in minimum bias proton--proton and central nucleus--nucleus collisions at momenta between 2.8 and 400 GeV/c per nucleon have been compiled. The multiplicities for nucleon--nucleon interactions were constructed. The ratios of strange particle multiplicity to participant nucleon as well as to pion multiplicity are larger for central nucleus--nucleus collisions than for nucleon--nucleon interactions at all studied energies. The data at AGS energies suggest that the latter ratio saturates with increasing masses of the colliding nuclei. The strangeness to pion multiplicity ratio observed in nucleon--nucleon interactions increases with collision energy in the whole energy range studied. A qualitatively different behaviour is observed for central nucleus--nucleus collisions: the ratio rapidly increases when going from Dubna to AGS energies and changes little between AGS and SPS energies. This change in the behaviour can be related to the increase in the entropy production observed in central nucleus-nucleus collisions at the same energy range. The results are interpreted within a statistical approach. They are consistent with the hypothesis that the Quark Gluon Plasma is created at SPS energies, the critical collision energy being between AGS and SPS energies.

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Pion multiplicity in nuclear collisions

Gazdzicki, M. ; Roehrich, D. ;
Z.Phys.C 65 (1995) 215-223, 1995.
Inspire Record 398172 DOI 10.17182/hepdata.14107

Data on the mean multiplicity ofπ- produced in minimum bias proton-proton, proton-neutron and proton-nucleus interactions as well as central nucleus-nucleus collisions at momenta of 1.4–400 GeV/c per nucleon have been compiled and studied. The results for neutron-neutron and nucleon-nucleon interactions were then constructed. The dependence of the mean pion multiplicity in proton-nucleus interactions and central collisions of identical nuclei are studied as a function of the collision energy and the nucleus mass number. The number of produced pions per participant nucleon in central collisions of identical nuclei is found to be independent of the number of participants at a fixed incident momentum per nucleon. The mean multiplicity of negatively charged hadrons per participant nucleon for central nucleus-nucleus collisions is lower by about 0.12 than the corresponding multiplicity for nucleon-nucleon interactions atpLAB≲15 A·GeV/c, whereas the result at 200 A·GeV/c is above the corresponding nucleon-nucleon multiplicity. This may indicate change of the collision dynamics at high energy.

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Proton-proton collisions at 19.8 GeV/c

Abraham, F.F. ; Kalbach, R.M. ;
Nuovo Cim. 26 (1962) 717-728, 1962.
Inspire Record 1185008 DOI 10.17182/hepdata.37715

Elastic and inelastic 19.8 GeV/c proton-proton collisions in nuclear emulsion are examined using an external proton beam of the CERN Proton Synchrotron. Multiple scattering, blob density, range and angle measurements give the momentum spectra and angular distributions of secondary protons and pions. The partial cross-sections corresponding to inelastic interactions having two, four, six, eight, ten and twelve charged secondaries are found to be, respectively, (16.3±8.4) mb, (11.5 ± 6.0) mb, (4.3 ± 2.5) mb, (1.9 ± 1.3) mb, (0.5 ± 0.5) mb and (0.5±0.5)mb. The elastic cross-section is estimated to be (4.3±2.5) mb. The mean charged meson multiplicity for inelastic events is 3.7±0.5 and the average degree of inelasticity is 0.35±0.09. Strong forward and backward peaking is observed in the center-of-mass system for both secondary charged pions and protons. Distributions of energy, momentum and transverse momentum for identified charged secondaries are presented and compared with the results of work at other energies and with the results of a statistical theory of proton-proton collisions.

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High $p_T$ Hadron Production in Photon - Photon Collisions

The TASSO collaboration Brandelik, R. ; Braunschweig, W. ; Gather, K. ; et al.
Phys.Lett.B 107 (1981) 290-296, 1981.
Inspire Record 167417 DOI 10.17182/hepdata.31027

We have studied the properties of hadron production in photon-photon scattering with tagged photons at the e + e − storage ring PETRA. A tail in the p T distribution of particles consistent with p T −4 has been observed. We show that this tail cannot be due to the hadronic part of the photon. Selected events with high p T particles are found to be consistent with a two-jet structure as expected from a point-like coupling of the photons to quarks. The lowest-order cross section predicted for γγ → q q , σ = 3 Σ e q 4 · σ γγ → μμ , is approached from above by the data at large transverse momenta.

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Evidence for Collective Multiparticle Correlations in p-Pb Collisions

The CMS collaboration Khachatryan, Vardan ; Sirunyan, Albert M ; Tumasyan, Armen ; et al.
Phys.Rev.Lett. 115 (2015) 012301, 2015.
Inspire Record 1345262 DOI 10.17182/hepdata.67530

The second-order azimuthal anisotropy Fourier harmonics, v2, are obtained in pPb and PbPb collisions over a wide pseudorapidity (eta) range based on correlations among six or more charged particles. The pPb data, corresponding to an integrated luminosity of 35 inverse nanobarns, were collected during the 2013 LHC pPb run at a nucleon-nucleon center-of-mass energy of 5.02 TeV by the CMS experiment. A sample of semi-peripheral PbPb collision data at sqrt(s[NN])= 2.76 TeV, corresponding to an integrated luminosity of 2.5 inverse microbarns and covering a similar range of particle multiplicities as the pPb data, is also analyzed for comparison. The six- and eight-particle cumulant and the Lee-Yang zeros methods are used to extract the v2 coefficients, extending previous studies of two- and four-particle correlations. For both the pPb and PbPb systems, the v2 values obtained with correlations among more than four particles are consistent with previously published four-particle results. These data support the interpretation of a collective origin for the previously observed long-range (large Delta[eta]) correlations in both systems. The ratios of v2 values corresponding to correlations including different numbers of particles are compared to theoretical predictions that assume a hydrodynamic behavior of a pPb system dominated by fluctuations in the positions of participant nucleons. These results provide new insights into the multi-particle dynamics of collision systems with a very small overlapping region.

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Charged particle multiplicities in nuclear collisions at 200-GeV/N

The NA35 collaboration Bächler, J. ; Bartke, J. ; Bialkowska, H. ; et al.
Z.Phys.C 51 (1991) 157-162, 1991.
Inspire Record 320907 DOI 10.17182/hepdata.14983

Data on multiplicities of charged particles produced in proton-nucleus and nucleus-nucleus collisions at 200 GeV per nucleon are presented. It is shown that the mean multiplicity of negative particles is proportional to the mean number of nucleons participating in the collision both for nucleus-nucleus and proton-nucleus collisions. The apparent consistency of pion multiplicity data with the assumption of an incoherent superposition of nucleon-nucleon collisions is critically discussed.

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One pion production in pp collisions at 16.2 gev/c

Gnat, Y. ; Alexander, G. ; Benary, O. ; et al.
Nucl.Phys.B 54 (1973) 333-354, 1973.
Inspire Record 84174 DOI 10.17182/hepdata.32585

A study of pp interactions at an incident momentum of 16.2 GeV/ c leading to two-prong non-strange final states was carried out in an exposure of the 2m CERN hydrogen bubble chamber. The c.m. angle and momentum distributions for the outgoing particles in the final states pn π + and pp π 0 are presented and discussed. These final states were analysed in terms of quasi two-body final states - N(Nπ), with the pion-nucleon system in an I = 1 2 or I = 3 2 state. A determination of these two isospin amplitudes and their interference term is then carried out. The reaction pp → pn π + is found to be well described by a Reggeized exchange model, as well as by a double Regge-exchange model.

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Observation of significant spin effects in hard collisions at 40-GeV/c

Apokin, V.D. ; Arestov, Yu.I. ; Astafev, O.V. ; et al.
Phys.Lett.B 243 (1990) 461-464, 1990.
Inspire Record 303587 DOI 10.17182/hepdata.29694

A single-spin asymmetry in the inclusive π 0 production at small x F was measured. In the experiment 40 GeV/c π − mesons were incident on transversely polarized protons and deutrons. An asymmetry of (40–50)% has been revealed in the hard scattering region.

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Inclusive pi- and gamma Production in 24-GeV/c p p Collisions

Beier, E.W. ; Raychaudhuri, K. ; Takeda, H. ; et al.
Phys.Rev.Lett. 37 (1976) 1114-1116, 1976.
Inspire Record 115982 DOI 10.17182/hepdata.21087

We report the 24-GeV/c inclusive π− yield near θc.m.=90° for 0.5<~PT≲2.2 GeV/c. No high-PT excess is seen at this energy. In addition we have obtained the inclusive γ-ray yield from a measurement of low-mass e+e− pairs. This yield is compared with that expected from π0-, η-, and ω-meson decay, to provide limits on possible direct photon production.

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Low Mass Electron Pair Anomaly in 17-{GeV}/c $\pi^- P$ Collisions

Stekas, J. ; Abshire, G. ; Adams, M.R. ; et al.
Phys.Rev.Lett. 47 (1981) 1686-1689, 1981.
Inspire Record 172147 DOI 10.17182/hepdata.20624

Inclusive e+e− production in 17-GeV/c π−p collisions has been measured. An excess of e+e− pairs over those from known sources for 0.1<~mee<~0.6 GeV and x<0.5 was found. No evidence is found for enhancements in specific final states involving electrons and photons or charged particles. The photon multiplicity associated with these pairs is measured.

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Pion Production at High Transverse Momentum in 24-{GeV} Proton Proton Collisions

Beier, E.W. ; Patton, R. ; Raychaudhuri, K. ; et al.
Phys.Rev.D 18 (1978) 2235, 1978.
Inspire Record 7054 DOI 10.17182/hepdata.24372

We report measurements of the inclusive π− and π+ yields in 24-GeV proton-proton collisions at θc.m.=90° for 2.2≤PT≤2.8 GeV/c. There is a high-PT deficit, rather than excess, at this incident energy.

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Inclusive $J/\psi$ production in $pp$ collisions at $\sqrt{s} = 2.76$ TeV

The ALICE collaboration Abelev, B. ; Adam, J. ; Adamova, D. ; et al.
Phys.Lett.B 718 (2012) 295-306, 2012.
Inspire Record 1094079 DOI 10.17182/hepdata.62231

The ALICE Collaboration has measured inclusive J/psi production in pp collisions at a center of mass energy sqrt(s)=2.76 TeV at the LHC. The results presented in this Letter refer to the rapidity ranges |y|<0.9 and 2.5<y<4 and have been obtained by measuring the electron and muon pair decay channels, respectively. The integrated luminosities for the two channels are L^e_int=1.1 nb^-1 and L^mu_int=19.9 nb^-1, and the corresponding signal statistics are N_J/psi^e+e-=59 +/- 14 and N_J/psi^mu+mu-=1364 +/- 53. We present dsigma_J/psi/dy for the two rapidity regions under study and, for the forward-y range, d^2sigma_J/psi/dydp_t in the transverse momentum domain 0<p_t<8 GeV/c. The results are compared with previously published results at sqrt(s)=7 TeV and with theoretical calculations.

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Multiple Pion Production in pi-Ne Collisions at 10.5-GeV and 200-GeV

Elliott, J.R. ; Fortney, L.R. ; Goshaw, A.T. ; et al.
Phys.Rev.Lett. 34 (1975) 607, 1975.
Inspire Record 2065 DOI 10.17182/hepdata.31340

We have measured the multiplicities of pions produced in the collisions of π mesons with neon nuclei at bombarding momenta of 10.5 and 200 GeV/c. The diffractive production of pions is clearly separable. If one excludes the diffractive part, the pion multiplicity obeys the same Koba-Nielsen-Olesen scaling as found previously for π−−p collisions. This fact would seem to indicate the validity of an energy-flux or collective-variable description of the production process. A surprisingly large number of energetic protons (> 1 GeV/c lab momentum) are found to be produced in π-Ne collisions.

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Study of $\omega \omega$ Systems Produced in 38-{GeV}/$c \pi^- p$ Collisions

The IHEP-IISN-LANL-LAPP-TSUIHEP collaboration Alde, D. ; Binon, F.G. ; Bricman, C. ; et al.
Phys.Lett.B 216 (1989) 451, 1989.
Inspire Record 267049 DOI 10.17182/hepdata.29857

The π − p→ ωω n reaction has studied for the first time at the 70 GeV IHEP accelerator. The six photons from the decay of the two ω mesons were detected in GAMS-2000, a hodoscope multi-photon spectometer. Two resonances decaying into ωω,X (1640) and X(1960), have been observed. Their quantum numbers are J PC =2 ++ , I G =0 + . The reaction is dominated by the one-pion exchange mechanism. The production cross sections σ. BR(X→ ωω ) are 0.65±0.15 μ b and 1.0±0.2 μ b, respectively.

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Jet fragmentation properties of $\bar{p}p$ collisions at $\sqrt{s} = 1.8$ TeV

The CDF collaboration Abe, F. ; Amidei, D. ; Apollinari, G. ; et al.
Phys.Rev.Lett. 65 (1990) 968-971, 1990.
Inspire Record 297585 DOI 10.17182/hepdata.19919

The charged-particle fractional momentum distribution within jets, D(z), has been measured in dijet events from 1.8-TeV p¯p collisions in the Collider Detector at Fermilab. As expected from scale breaking in quantum chromodynamics, the fragmentation function D(z) falls more steeply as dijet invariant mass increases from 60 to 200 GeV/c2. The average fraction of the jet momentum carried by charged particles is 0.65±0.02(stat)±0.08(syst).

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Measurement of the Transverse Momentum of Dielectron Pairs in Proton - Anti-Proton Collisions

Casey, Dylan Patrick ; Ferbel, Thomas ;
PhD Thesis, Rochester U., 1997.
Inspire Record 454166 DOI 10.17182/hepdata.18470

We present a measurement of the transverse momentum distribution of dielectron pairs with invariant mass near the mass of the Z boson. The data were obtained using the DO detector during the 1994-1995 run of the Tevatron Co!lider at Fermilab. The data used in the measurement corresponds to an integrated luminosity of 108.5 $pb^{-1}$ The measurement is compared to current phenomenology for vector boson production in proton-antiproton interactions, and the results are found to be consistent with expectation from Quantum Chromodynamics (QCD).

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Multi - Pion System Production in Pion - Nucleon Collisions at $p$ = 40-{GeV}/c

Angelov, N.S. ; Grishin, V.G. ; Kvatadze, R.A. ;
Yad.Fiz. 32 (1980) 1342-1350, 1980.
Inspire Record 153217 DOI 10.17182/hepdata.17933
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Nuclear excitation and multiple production in proton-nucleon collisions at CERN-PS energies

Cvijanovich, G. ; Dayton, B. ; Egli, P. ; et al.
Nuovo Cim. 20 (1961) 1012-1016, 1961.
Inspire Record 1185004 DOI 10.17182/hepdata.1108
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Global $\Lambda$ hyperon polarization in nuclear collisions: evidence for the most vortical fluid

The STAR collaboration Adamczyk, L. ; Adkins, J.K. ; Agakishiev, G. ; et al.
Nature 548 (2017) 62-65, 2017.
Inspire Record 1510474 DOI 10.17182/hepdata.77494

The extreme temperatures and energy densities generated by ultra-relativistic collisions between heavy nuclei produce a state of matter with surprising fluid properties. Non-central collisions have angular momentum on the order of 1000$\hbar$, and the resulting fluid may have a strong vortical structure that must be understood to properly describe the fluid. It is also of particular interest because the restoration of fundamental symmetries of quantum chromodynamics is expected to produce novel physical effects in the presence of strong vorticity. However, no experimental indications of fluid vorticity in heavy ion collisions have so far been found. Here we present the first measurement of an alignment between the angular momentum of a non-central collision and the spin of emitted particles, revealing that the fluid produced in heavy ion collisions is by far the most vortical system ever observed. We find that $\Lambda$ and $\overline{\Lambda}$ hyperons show a positive polarization of the order of a few percent, consistent with some hydrodynamic predictions. A previous measurement that reported a null result at higher collision energies is seen to be consistent with the trend of our new observations, though with larger statistical uncertainties. These data provide the first experimental access to the vortical structure of the "perfect fluid" created in a heavy ion collision. They should prove valuable in the development of hydrodynamic models that quantitatively connect observations to the theory of the Strong Force. Our results extend the recent discovery of hydrodynamic spin alignment to the subatomic realm.

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One, Two and Three Pion Production in p d Collisions at 19-GeV/c

The Scandinavian Bubble Chamber collaboration Bakken, V. ; Gennow, H. ; Jacobsen, T. ; et al.
Nucl.Phys.B 124 (1977) 229-254, 1977.
Inspire Record 111511 DOI 10.17182/hepdata.35429

We present cross sections for coherent and non-coherent production of one, two and three pions in pd reactions at 19 GeV/ c . The mass distributions of the two pion non-coherent channels are studied. Strong single Δ(1236) and also some double Δ production is observed. Clear evidence for ϱ production is seen.

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Charged Particle Spectra in $\alpha \alpha$ and $\alpha p$ Collisions at the {CERN} {ISR}

The CERN-Heidelberg-Lund collaboration Bell, W. ; Braune, K. ; Glaesson, G. ; et al.
Z.Phys.C 27 (1985) 191, 1985.
Inspire Record 205679 DOI 10.17182/hepdata.16095

Momenta of charged particles produced in inelastic αα, αp, andpp collisions were measured using the Split-Field-Magnet detector at the CERN Intersecting Storage Rings. Inclusive and semi-in-clusive spectra are presented as a function of rapidityy, Feynman-x, and transverse momentumpT. The inclusivey distributions agree well with predictions of the dual parton model; the highest particle densities are reached aty≃0 and the momenta of leading protons decrease significantly for increasing total multiplicity. ‘Temperatures’ are equal in αα, αp, andpp interactions. ThepT distributions depend weakly on the multiplicity.

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Study of $t\bar{t}$ production $p\bar{p}$ collisions using total transverse energy

The CDF collaboration Abe, F. ; Akimoto, H. ; Akopian, A. ; et al.
Phys.Rev.Lett. 75 (1995) 3997, 1995.
Inspire Record 396003 DOI 10.17182/hepdata.42358

We analyze a sample of W + jet events collected with the Collider Detector at Fermilab (CDF) in ppbar collisions at sqrt(s) = 1.8 TeV to study ttbar production. We employ a simple kinematical variable "H", defined as the scalar sum of the transverse energies of the lepton, neutrino and jets. For events with a W boson and four or more jets, the shape of the "H" distribution deviates by 3.8 standard deviations from that expected from known backgrounds to ttbar production. However this distribution agrees well with a linear combination of background and ttbar events, the agreement being best for a top mass of 180 GeV/c^2.

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The Dubna-Alma Ata-Yerevan-Helsinki-Moscow-Prague-Tbilisi collaboration Batyunya, B.V. ; Boguslavsky, I.V. ; Gramenitsky, I.M. ; et al.
Sov.J.Nucl.Phys. 37 (1983) 58, 1983.
Inspire Record 178090 DOI 10.17182/hepdata.71073
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Small angle $J/\psi$ production in $p\bar{p}$ collisions at $\sqrt{s} = 1.8$ TeV

The D0 collaboration Abbott, B. ; Abolins, M. ; Abramov, V. ; et al.
Phys.Rev.Lett. 82 (1999) 35-40, 1999.
Inspire Record 473954 DOI 10.17182/hepdata.42141

This paper presents the first measurement of the inclusive J/Psi production cross section in the forward pseudorapidity region 2.5<|eta|<3.7 in ppbar collisions at sqrt(s)=1.8TeV. The results are based on 9.8 pb-1 of data collected using the D0 detector at the Fermilab Tevatron Collider. The inclusive J/Psi cross section for transverse momenta between 1 and 16 GeV/c is compared with theoretical models of charmonium production.

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The inclusive jet cross section in $\bar{p}p$ collisions at $\sqrt{s} = 1.8$ TeV

The D0 collaboration Abbott, B. ; Abolins, M. ; Abramov, V. ; et al.
Phys.Rev.Lett. 82 (1999) 2451-2456, 1999.
Inspire Record 473457 DOI 10.17182/hepdata.42154

We have made a precise measurement of the central inclusive jet cross section at sqrt(s) = 1.8 TeV. The measurement is based on an integrated luminosity of 92 pb-1 collected at the Fermilab Tevatron pbar-p Collider with the D-Zero detector. The cross section, reported as a function of jet transverse energy (ET >= 60 GeV) in the pseudorapidity interval |eta| <= 0.5, is in good agreement with predictions from next-to-leading order quantum chromodynamics.

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