559 research outputs found
Harmonic moments of the gluon density distribution in AA collisions
By using Monte-Carlo implementations of -factorization formula with
running-coupling BK unintegrated gluon distributions for nucleus-nucleus
collisions, we compute higher order harmonic moments of the initial density
distribution for both RHIC(Au+Au@200GeV) and LHC([email protected]) collisions. We
study their sensitivity to the size of the valence parton distribution in the
nucleon.Comment: 4 pages, 2 figures, references added, figure 2 is replaced by the
results of central collision
3D Jet Tomography of Twisted Strongly Coupled Quark Gluon Plasmas
The triangular enhancement of the rapidity distribution of hadrons produced
in p+A reactions relative to p+p is a leading order in A^{1/3}/log(s) violation
of longitudinal boost invariance at high energies. In A+A reactions this leads
to a trapezoidal enhancement of the local rapidity density of produced gluons.
The local rapidity gradient is proportional to the local participant number
asymmetry, and leads to an effective rotation in the reaction plane. We propose
that three dimensional jet tomography, correlating the long range rapidity and
azimuthal dependences of the nuclear modification factor,
R_{AA}(\eta,\phi,p_\perp; b>0), can be used to look for this intrinsic
longitudinal boost violating structure of collisions to image the
produced twisted strongly coupled quark gluon plasma (sQGP). In addition to
dipole and elliptic azimuthal moments of R_{AA}, a significant high p_\perp
octupole moment is predicted away from midrapidity. The azimuthal angles of
maximal opacity and hence minima of R_{AA} are rotated away from the normal to
the reaction plane by an `Octupole Twist' angle, \theta_3(\eta), at forward
rapidities.Comment: 10 Pages, 16 Figures, RevTex, Replaced with Peer reviewed verion for
PR
The eccentricity in heavy-ion collisions from Color Glass Condensate initial conditions
The eccentricity in coordinate-space at midrapidity of the overlap zone in
high-energy heavy-ion collisions predicted by the -factorization
formalism is generically larger than expected from scaling with the number of
participants. We provide a simple qualitative explanation of the effect which
shows that it is not caused predominantly by edge effects. We also show that it
is quite insensitive to ``details'' of the unintegrated gluon distribution
functions such as the presence of leading-twist shadowing and of an extended
geometric scaling window. The larger eccentricity increases the azimuthal
asymmetry of high transverse momentum particles. Finally, we point out that the
longitudinal structure of the Color Glass Condensate initial condition for
hydrodynamics away from midrapidity is non-trivial but requires understanding
of large- effects.Comment: 8 pages, 7 figures; v3: added note regarding Qs2~n_part versus
Qs2~T_A, final version to appear in PR
Collective flow from AA, pA to pp collisions - Toward a unified paradigm
I give an overview of the latest development in understanding collective
phenomena in high-multiplicity hadronic final state from relativistic
nucleus-nucleus, proton-nucleus and proton-proton collisions. Upon reviewing
the experimental data and confronting them with theoretical models, a unified
paradigm in describing the observed collectivity across all hadronic collision
systems is emerging. Potential future paths toward addressing key open
questions, especially on collectivity in small systems (pp, pA), are discussed.Comment: 9 pages, 6 figures, plenary contribution to Quark Matter 2017,
February 5-11 (2017), Chicago (IL), US
The Hot QCD White Paper: Exploring the Phases of QCD at RHIC and the LHC
The past decade has seen huge advances in experimental measurements made in
heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) and more
recently at the Large Hadron Collider (LHC). These new data, in combination
with theoretical advances from calculations made in a variety of frameworks,
have led to a broad and deep knowledge of the properties of thermal QCD matter.
Increasingly quantitative descriptions of the quark-gluon plasma (QGP) created
in these collisions have established that the QGP is a strongly coupled liquid
with the lowest value of specific viscosity ever measured. However, much
remains to be learned about the precise nature of the initial state from which
this liquid forms, how its properties vary across its phase diagram and how, at
a microscopic level, the collective properties of this liquid emerge from the
interactions among the individual quarks and gluons that must be visible if the
liquid is probed with sufficiently high resolution. This white paper, prepared
by the Hot QCD Writing Group as part of the U.S. Long Range Plan for Nuclear
Physics, reviews the recent progress in the field of hot QCD and outlines the
scientific opportunities in the next decade for resolving the outstanding
issues in the field.Comment: 110 pages, 33 figures, 429 references. Prepared as part of the U.S.
Long-Range Plan for Nuclear Physic
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