Dihadron correlations are analyzed in $\sqrt{s_{_{\rm NN}}} = 200$ GeV $d$+Au collisions classified by forward charged particle multiplicity and zero-degree neutral energy in the Au-beam direction. ...It is found that the jetlike correlated yield increases with the event multiplicity. After taking into account this dependence, the non-jet contribution on the away side is minimal, leaving little room for a back-to-back ridge in these collisions.
We report measurements of forward jets produced in Cu+Au collisions at \(\sqrt{s_{NN}}=200\) GeV at the Relativistic Heavy Ion Collider. The jet-energy distributions extend to energies much larger ...than expected by Feynman scaling. This constitutes the first clear evidence for Feynman-scaling violations in heavy-ion collisions. Such high-energy particle production has been in models via QCD string interactions, but so far is untested by experiment. One such model calls this a hadronic accelerator. Studies with a particular heavy-ion event generator (HIJING) show that photons and mesons exhibit such very high-energy production in a heavy-ion collision, so {\it QCD accelerator} appropriately captures the physics associated with such QCD string interactions. All models other than HIJING used for hadronic interactions in the study of extensive air showers from cosmic rays either do not include these QCD string interactions, or have smaller effects from the QCD accelerator.
DISTO data on K − p p Maggiora, M.; Kienle, P.; Suzuki, K. ...
Nuclear physics. A,
04/2010, Letnik:
835, Številka:
1
Journal Article
Recenzirano
The data from the DISTO Collaboration on the exclusive
p
p
→
p
K
+
Λ
production acquired at
T
p
=
2.85
GeV
have been re-analysed in order to search for a deeply bound
K
−
p
p
(
≡
X
)
state, to be ...formed in the binary process
p
p
→
K
+
X
. The
preliminary spectra of the
Δ
M
K
+
missing-mass and of the
M
p
Λ
invariant-mass show, for large transverse-momenta of protons and kaons, a distinct broad peak with a mass
M
X
=
2265
±
2
MeV
/
c
2
and a width
Γ
X
=
118
±
8
MeV
/
c
2
.
We report the first three-particle coincidence measurement in pseudorapidity (Δη) between a high transverse momentum (p⊥) trigger particle and two lower p⊥ associated particles within azimuth ...|Δϕ|<0.7 in square root of s(NN)=200 GeV d+Au and Au+Au collisions. Charge ordering properties are exploited to separate the jetlike component and the ridge (long range Δη correlation). The results indicate that the correlation of ridge particles are uniform not only with respect to the trigger particle but also between themselves event by event in our measured Δη. In addition, the production of the ridge appears to be uncorrelated to the presence of the narrow jetlike component.
Global polarization of Ξ and Ω hyperons has been measured for the first time in Au+Au collisions at sqrts_{NN}=200 GeV. The measurements of the Ξ^{-} and Ξover ¯^{+} hyperon polarization have been ...performed by two independent methods, via analysis of the angular distribution of the daughter particles in the parity violating weak decay Ξ→Λ+π, as well as by measuring the polarization of the daughter Λ hyperon, polarized via polarization transfer from its parent. The polarization, obtained by combining the results from the two methods and averaged over Ξ^{-} and Ξover ¯^{+}, is measured to be ⟨P_{Ξ}⟩=0.47±0.10(stat)±0.23(syst)% for the collision centrality 20%-80%. The ⟨P_{Ξ}⟩ is found to be slightly larger than the inclusive Λ polarization and in reasonable agreement with a multiphase transport model. The ⟨P_{Ξ}⟩ is found to follow the centrality dependence of the vorticity predicted in the model, increasing toward more peripheral collisions. The global polarization of Ω, ⟨P_{Ω}⟩=1.11±0.87(stat)±1.97(syst)% was obtained by measuring the polarization of daughter Λ in the decay Ω→Λ+K, assuming the polarization transfer factor C_{ΩΛ}=1.
We present ΛΛ correlation measurements in heavy-ion collisions for Au+Au collisions at sqrts_{NN}=200 GeV using the STAR experiment at the Relativistic Heavy-Ion Collider. The Lednický-Lyuboshitz ...analytical model has been used to fit the data to obtain a source size, a scattering length and an effective range. Implications of the measurement of the ΛΛ correlation function and interaction parameters for dihyperon searches are discussed.
We report K/pi fluctuations from Au + Au collisions at sqrts(NN)= 19.6, 62.4, 130, and 200 GeV using the STAR detector at the Relativistic Heavy Ion Collider. K/pi fluctuations in central collisions ...show little dependence on incident energy and are on the same order as those from NA49 at the Super Proton Synchrotron in central Pb + Pb collisions at sqrts(NN)=12.3 and 17.3 GeV. We report results for the collision centrality dependence of K/pi fluctuations and results for charge-separated fluctuations. We observe that the K/pi fluctuations scale with the charged particle multiplicity density.
We report the first measurement of charmed-hadron (D(0)) production via the hadronic decay channel (D(0) → K(-) + π(+)) in Au+Au collisions at sqrts(NN) = 200 GeV with the STAR experiment. The charm ...production cross section per nucleon-nucleon collision at midrapidity scales with the number of binary collisions, N(bin), from p+p to central Au+Au collisions. The D(0) meson yields in central Au + Au collisions are strongly suppressed compared to those in p+p scaled by N(bin), for transverse momenta p(T) > 3 GeV/c, demonstrating significant energy loss of charm quarks in the hot and dense medium. An enhancement at intermediate p(T) is also observed. Model calculations including strong charm-medium interactions and coalescence hadronization describe our measurements.
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