Measurements of inclusive spectra and mean multiplicities of
π
±
, K
±
, p and
p
¯
produced in inelastic p + p interactions at incident projectile momenta of 20, 31, 40, 80 and 158
GeV
/
c
(
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.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We present recent results obtained by the BRAHMS experiment at the Relativistic Heavy Ion Collider (RHIC) for the systems of Au+Au and Cu+Cu at
s
NN
=
200
GeV
and at 62.4 GeV, and p+p at
s
NN
=
200
... GeV
. BRAHMS explores reaction dynamics and properties of the hot and high energy density matter produced in ultra-relativistic heavy-ion collisions versus its longitudinal expansion. Overall charged-particle production and particle spectra over a large rapidity interval and
p
T
range are presented. Nuclear modification factors for Au+Au and Cu+Cu collisions are discussed. The observed number of charged particles produced per unit of rapidity in the central rapidity region indicates that a high energy density system is produced at the initial stage of the Au+Au reaction. Analysis of anti-particle to particle ratios as a function of rapidity and collision energy reveal that particle populations at the chemical freeze-out stage for heavy-ion reactions at and above SPS energies are controlled by the baryon chemical potential. From the particle spectra we deduce significant radial expansion (
β
≈
0.75
), as expected for systems created with a large initial energy density. We also measure the elliptic flow parameter
v
2
versus rapidity and
p
T
. A weak dependence on rapidity of the
p
T
differential
v
2
is observed. We present rapidity dependent
p
/
π
ratios within
0
<
y
<
3
for Au+Au and Cu+Cu at
s
NN
=
200
GeV
. The ratios are enhanced in nucleus-nucleus collisions as compared to p+p collisions. The particle ratios are discussed in terms of their system size and rapidity dependence. We compare
R
AA
for Au+Au at
s
NN
=
200
GeV
and at 62.4 GeV, and for Au+Au and Cu+Cu at
s
NN
=
200
GeV
.
R
AA
is found to increase with decreasing collision energy, decreasing system size, and when going towards more peripheral collisions. However,
R
AA
shows only a very weak dependence on rapidity (for
0
<
y
<
3.2
), both for pions and protons.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The kinetic-energy variation of emitted light clusters has been employed as a clock to explore the time evolution of the temperature for thermalizing composite systems produced in the reactions of ...26A, 35A, and 47A MeV {sup 64}Zn with {sup 58}Ni, {sup 92}Mo, and {sup 197}Au. For each system investigated, the double-isotope ratio temperature curve exhibits a high maximum apparent temperature, in the range of 10-25 MeV, at high ejectile velocity. These maximum values increase with increasing projectile energy and decrease with increasing target mass. The time at which the maximum in the temperature curve is reached ranges from 80 to 130 fm/c after contact. For each different target, the subsequent cooling curves for all three projectile energies are quite similar. Temperatures comparable with those of limiting temperature systematics are reached 30 to 40 fm/c after the times corresponding to the maxima, at a time when antisymmetrized molecular dynamics transport model calculations predict entry into the final evaporative or fragmentation stage of deexcitation of the hot composite systems. Evidence for the establishment of thermal and chemical equilibrium is discussed.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
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
(
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.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Measurements of the
π
±
,
K
±
, and proton double differential yields emitted from the surface of the 90-
cm
-long carbon target (T2K replica) were performed for the incoming
31
GeV
/
c
protons with ...the NA61/SHINE spectrometer at the CERN SPS using data collected during 2010 run. The double differential
π
±
yields were measured with increased precision compared to the previously published NA61/SHINE results, while the
K
±
and proton yields were obtained for the first time. A strategy for dealing with the dependence of the results on the incoming proton beam profile is proposed. The purpose of these measurements is to reduce significantly the (anti)neutrino flux uncertainty in the T2K long-baseline neutrino experiment by constraining the production of (anti)neutrino ancestors coming from the T2K target.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The reactions {sup 12}C+{sup 116}Sn, {sup 22}Ne+Ag, {sup 40}Ar+{sup 100}Mo, and {sup 64}Zn+{sup 89}Y have been studied at 47A MeV projectile energy. For these reactions the most violent collisions ...lead to increasing amounts of fragment and light particle emission as the projectile mass increases. This is consistent with quantum molecular dynamics (QMD) model simulations of the collisions. Moving source fits to the light charged particle data have been used to gain a global view of the evolution of the particle emission. Comparisons of the multiplicities and spectra of light charged particles emitted in the reactions with the four different projectiles indicate a common emission mechanism for early emitted ejectiles even though the deposited excitation energies differ greatly. The spectra for such ejectiles can be characterized as emission in the nucleon-nucleon frame. Evidence that the {sup 3}He yield is dominated by this type of emission and the role of the collision dynamics in determining the {sup 3}H/{sup 3}He yield ratio are discussed. Self-consistent coalescence model analyses are applied to the light cluster yields, in an attempt to probe emitter source sizes and to follow the evolution of the temperatures and densities from the time of first particle emission to equilibration. These analyses exploit correlations between ejectile energy and emission time, suggested by the QMD calculations. In this analysis the degree of expansion of the emitting system is found to increase with increasing projectile mass. The double isotope yield ratio temperature drops as the system expands. Average densities as low as 0.36{rho}{sub 0} are reached at a time near 100 fm/c after contact. Calorimetric methods were used to derive the mass and excitation energy of the excited nuclei which are present after preequilibrium emission. The derived masses range from 102 to 116 u and the derived excitation energies increase from 2.6 to 6.9 MeV/nucleon with increasing projectile mass. A caloric curve is derived for these expanded A{approx}110 nuclei. This caloric curve exhibits a plateau at temperatures near 7 MeV. The plateau extends from {approx}3.5 to 6.9 MeV/nucleon excitation energy. (c) 2000 The American Physical Society.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
Measurements of hadron production in p + C interactions at 31 GeV/
c
are performed using the NA61/SHINE spectrometer at the CERN SPS. The analysis is based on the full set of data collected in 2009 ...using a graphite target with a thickness of 4 % of a nuclear interaction length. Inelastic and production cross sections as well as spectra of
π
±
,
K
±
, p,
K
S
0
and
Λ
are measured with high precision. These measurements are essential for improved calculations of the initial neutrino fluxes in the T2K long-baseline neutrino oscillation experiment in Japan. A comparison of the NA61/SHINE measurements with predictions of several hadroproduction models is presented.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We review the main results obtained by the BRAHMS Collaboration on the properties of hot and dense hadronic and partonic matter produced in ultrarelativistic heavy ion collisions at RHIC. A ...particular focus of this paper is to discuss to what extent the results collected so far by BRAHMS, and by the other three experiments at RHIC, can be taken as evidence for the formation of a state of deconfined partonic matter, the so-called quark–gluon plasma (QGP). We also discuss evidence for a possible precursor state to the QGP, i.e., the proposed color glass condensate.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The NA61/SHINE experiment at the CERN Super Proton Synchrotron studies the onset of deconfinement in strongly interacting matter through a beam energy scan of particle production in collisions of ...nuclei of varied sizes. This paper presents results on inclusive double-differential spectra, transverse momentum and rapidity distributions and mean multiplicities of π±, K±, p and $\bar{ρ}$ produced in 40Ar + 45Sc collisions at beam momenta of 13A, 19A, 30A, 40A, 75A and 150A Ge V/c. The analysis uses the 10% most central collisions, where the observed forward energy defines centrality. The energy dependence of the K±/π+ ratios as well as of inverse slope parameters of the K± transverse mass distributions are placed in between those found in inelastic ρ + ρ and central Pb + Pb collisions. The results obtained here establish a system-size dependence of hadron production properties that so far cannot be explained either within statistical or dynamical models.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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