1,977 research outputs found
Conference Summary of QNP2018
This report is the summary of the Eighth International Conference on Quarks
and Nuclear Physics (QNP2018). Hadron and nuclear physics is the field to
investigate high-density quantum many-body systems bound by strong
interactions. It is intended to clarify matter generation of universe and
properties of quark-hadron many-body systems. The QNP is an international
conference which covers a wide range of hadron and nuclear physics, including
quark and gluon structure of hadrons, hadron spectroscopy, hadron interactions
and nuclear structure, hot and cold dense matter, and experimental facilities.
First, I introduce the current status of the hadron and nuclear physics field
related to this conference. Next, the organization of the conference is
explained, and a brief overview of major recent developments is discussed by
selecting topics from discussions at the plenary sessions. They include
rapidly-developing field of gravitational waves and nuclear physics, hadron
interactions and nuclear structure with strangeness, lattice QCD, hadron
spectroscopy, nucleon structure, heavy-ion physics, hadrons in nuclear medium,
and experimental facilities of EIC, GSI-FAIR, JLab, J-PARC, Super-KEKB, and
others. Nuclear physics is at a fortunate time to push various projects at
these facilities. However, we should note that the projects need to be
developed together with related studies in other fields such as gravitational
physics, astrophysics, condensed-matter physics, particle physics, and
fundamental quantum physics.Comment: 10 pages, LaTeX, 1 style file, 3 figure files, Proceedings of Eighth
International Conference on Quarks and Nuclear Physics (QNP2018), November
13-17, 2018, Tsukuba, Japa
Elliptic flow at large transverse momenta from quark coalescence
We show that hadronization via quark coalescence enhances hadron elliptic
flow at large pT relative to that of partons at the same transverse momentum.
Therefore, compared to earlier results based on covariant parton transport
theory, more moderate initial parton densities dN/d\eta(b=0) ~ 1500-3000 can
explain the differential elliptic flow v_2(pT) data for Au+Au reactions at
s^1/2=130 and 200 AGeV from RHIC. In addition, v2(pT) could saturate at about
50% higher values for baryons than for mesons. If strange quarks have weaker
flow than light quarks, hadron v_2 at high pT decreases with relative
strangeness content.Comment: Minor changes, extended discussion. To appear in PR
Low Freeze-out Temperature and High Collective Velocities in Relativistic Heavy-Ion Collisions
On the basis of a nine-parameter expanding source model that includes special
relativity, quantum statistics, resonance decays, and freeze-out on a realistic
hypersurface in spacetime, we analyze in detail invariant pi+, pi-, K+, and K-
one-particle multiplicity distributions and pi+ and K+ two-particle
correlations in nearly central collisions of Si + Au at a laboratory bombarding
energy per nucleon of 14.6 GeV/c. By considering separately the one-particle
data and the correlation data, we find that the central baryon density, nuclear
temperature, transverse collective velocity, longitudinal collective velocity,
and source velocity are determined primarily by one-particle multiplicity
distributions and that the transverse radius, longitudinal proper time, width
in proper time, and pion incoherence fraction are determined primarily by
two-particle correlations. By considering separately the pion data and the kaon
data, we find that although the pion freeze-out occurs somewhat later than the
kaon freeze-out, the 99% confidence-level error bars associated with the two
freeze-outs overlap. These and other detailed studies confirm our earlier
conclusion based on the simultaneous consideration of the pion and kaon
one-particle and correlation data that the freeze-out temperature is less than
100 MeV and that both the longitudinal and transverse collective
velocities--which are anti-correlated with the temperature--are substantial. We
also discuss the flaws in several previous analyses that yielded a much higher
freeze-out temperature of approximately 140 MeV for both this reaction and
other reactions involving heavier projectiles and/or higher bombarding
energies.Comment: 14 pages. RevTeX 3.1. Submitted to Physical Review C. PostScript
version available at http://t2.lanl.gov/publications/publications.html or at
ftp://t2.lanl.gov/pub/publications/lf
Overview of charm production at RHIC
In this presentation, I discussed a) the charm total cross-section and its
comparisons to measurements at other beam energies and pQCD calculations; b)
the semileptonic decay of charmed hadrons and the sensitivity of non-photonic
leptons to charm quark collective flow and freeze-out; c) semileptonic decayed
electron spectrum at high transverse momentum, its comparison to FONLL in p+p
and d+Au collisions, and heavy-quark energy loss in Au+Au collisions.Comment: 8 pages, 4 figures, overview talk at SQM2006: Strangeness in Quark
Matter Los Angeles, CA, Mar. 26-31, 2006; minor text changes and references
adde
Evidence of early multi-strange hadron freeze-out in high energy nuclear collisions
Recently reported transverse momentum distributions of strange hadrons
produced in Pb(158AGeV) on Pb collisions and corresponding results from the
relativistic quantum molecular dynamics (RQMD) approach are examined. We argue
that the experimental observations favor a scenario in which multi-strange
hadrons are formed and decouple from the system rather early at large energy
densities (around 1 GeV/fm). The systematics of the strange and non-strange
particle spectra indicate that the observed transverse flow develops mainly in
the late hadronic stages of these reactions.Comment: 4 pages, 4 figure
Low-mass e+e- pair production in 158 A GeV Pb-Au collisions at the CERN SPS, its dependence on multiplicity and transverse momentum
We report a measurement of low-mass electron pairs observed in 158
GeV/nucleon Pb-Au collisions. The pair yield integrated over the range of
invariant masses 0.2 < m < 2.0 GeV is enhanced by a factor of 3.5 +/- 0.4
(stat) +/- 0.9 (syst) over the expectation from neutral meson decays. As
observed previously in S-Au collisions, the enhancement is most pronounced in
the invariant-mass region 300-700 MeV. For Pb-Au we find evidence for a strong
increase of the enhancement with centrality. In addition, we show that the
enhancement covers a wide range in transverse momentum, but is largest at the
lowest observed pt.Comment: 17 pages, 4 figures, submitted to Phys.Lett.
Particle dependence of elliptic flow in Au+Au collisions at 200 GeV
The elliptic flow parameter () for and
has been measured at mid-rapidity in Au + Au collisions at
GeV by the STAR collaboration. The values for both
and saturate at moderate , deviating
from the hydrodynamic behavior observed in the lower region. The
saturated values and the scales where the deviation begins are
particle dependent. The particle-type dependence of shows features
expected from the hadronization of a partonic ellipsoid by coalescence of
co-moving quarks. These results will be discussed in relation to the nuclear
modification factor () which has also been measured for and
by the STAR collaboration.Comment: 6 pages, 3 figures, Strange Quark Matter 2003 Conference (SQM 2003):
updated with 2 figures from original talk that did not appear in the journa
Directed flow of antiprotons in Au+Au collisions at AGS
Directed flow of antiprotons is studied in Au+Au collisions at a beam
momentum of 11.5A GeV/c. It is shown that antiproton directed flow is
anti-correlated to proton flow. The measured transverse momentum dependence of
the antiproton flow is compared with predictions of the RQMD event generator.Comment: 16 pages, 6 figure
Semi-Hard Scattering Unraveled from Collective Dynamics by Two-Pion Azimuthal Correlations in 158 A GeV/c Pb + Au Collisions
Elliptic flow and two-particle azimuthal correlations of charged hadrons and
high- pions ( 1 GeV/) have been measured close to mid-rapidity in
158A GeV/ Pb+Au collisions by the CERES experiment. Elliptic flow ()
rises linearly with to a value of about 10% at 2 GeV/. Beyond
1.5 GeV/, the slope decreases considerably, possibly indicating
a saturation of at high . Two-pion azimuthal anisotropies for
1.2 GeV/ exceed the elliptic flow values by about 60% in mid-central
collisions. These non-flow contributions are attributed to near-side and
back-to-back jet-like correlations, the latter exhibiting centrality dependent
broadening.Comment: Submitted to Phys. Rev. Letters, 4 pages, 5 figure
e+e--pair production in Pb-Au collisions at 158 GeV per nucleon
We present the combined results on electron-pair production in 158 GeV/n
{Pb-Au} (= 17.2 GeV) collisions taken at the CERN SPS in 1995 and
1996, and give a detailed account of the data analysis. The enhancement over
the reference of neutral meson decays amounts to a factor of 2.31 for semi-central collisions (28%
) when yields are integrated over 200 MeV/ in
invariant mass. The measured yield, its stronger-than-linear scaling with
, and the dominance of low pair strongly suggest an
interpretation as {\it thermal radiation} from pion annihilation in the
hadronic fireball. The shape of the excess centring at 500
MeV/, however, cannot be described without strong medium modifications of
the meson. The results are put into perspective by comparison to
predictions from Brown-Rho scaling governed by chiral symmetry restoration, and
from the spectral-function many-body treatment in which the approach to the
phase boundary is less explicit.Comment: 39 pages, 40 figures, to appear in Eur.Phys.J.C. (2005
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