1,865 research outputs found
Bottomonium production in heavy-ion collisions at STAR
Bottomonium measurements provide unique insight into hot and cold nuclear
matter effects present in the medium that is formed in high-energy heavy-ion
collisions. Recent STAR results show that in = 200 GeV central
Au+Au collisions the (1S) state is suppressed more than if only cold
nuclear matter effects were present, and the excited state yields are
consistent with a complete suppression. In 2012, STAR also collected 263.4
b high-energy-electron triggered data in U+U collisions at
= 193 GeV. Central U+U collisions, with an estimated 20% higher
energy density than in central Au+Au data, extend the (1S+2S+3S) and
Upsilon(1S) nuclear modification trends observed in Au+Au towards higher number
of participant nucleons, and confirm the suppression of the (1S)
state. We see a hint with 1.8 sigma significance that the (2S+3S)
excited states are not completely suppressed in U+U collisions. These data
support the sequential in-medium quarkonium dissociation picture and favor
models with a strong binding.Comment: Proceedings of the Hard Probes International Conference 2015,
Montreal, Canada. 4 pages, 5 figure
Neutral pion production in Au+Au collisions at RHIC
New results from the 2010 RHIC low energy program show a substantial
suppression of neutral pions in central Au+Au collisions at both sqrt{s_NN}=39
and 62.4 GeV c.m.s. energies. At high pT the 62.4 GeV and 200 GeV data follow
the same suppression pattern. On the other hand, otherwise successful pQCD
predictions do not describe the 39 GeV data. These observations indicate that
initial state effects may play a dominant role at smaller c.m.s. energies and
at lower pT . The azimuthal dependence of the nuclear modification factor R_AA
is strongly correlated with the (approximately elliptical) geometry of the
overlap region. The dependence of R_AA on the reaction plane, determined up to
pT=20 GeV/c from 2007 high-luminosity sqrt{s_NN}=200 GeV Au+Au data provides
great selectivity among theories, and favours the ASW scenario with AdS/CFT
correspondence over the pQCD-based models.Comment: Accepted for the Proceedings of Hard Probe 2012, Cagliary, Italy (4
pages, 4 figures
Production of Quarkonia at RHIC
The production of different quarkonium states provides unique insight to the
hot and cold nuclear matter effects in the strongly interacting medium that is
formed in high energy heavy ion collisions. While LHC explores the energy
frontier, RHIC has a broad physics program to explore the nuclear modification
at different energies in a wide range of systems. Some of the most interesting
recent results on and production in p+p, d+Au and A+A
collisions from PHENIX and STAR are summarized in this work.Comment: Writeup of the talk on the "Joint Wigner-CCNU High-Energy Heavy-Ion
Balaton Workshop 2015", Tihany, Hungary. To be published in the Gribov 85
memorial issue "Exploring Quantum Field Theory". 8 pages, 8 figure
Bond dimension witnesses and the structure of homogeneous matrix product states
For the past twenty years, Matrix Product States (MPS) have been widely used
in solid state physics to approximate the ground state of one-dimensional spin
chains. In this paper, we study homogeneous MPS (hMPS), or MPS constructed via
site-independent tensors and a boundary condition. Exploiting a connection with
the theory of matrix algebras, we derive two structural properties shared by
all hMPS, namely: a) there exist local operators which annihilate all hMPS of a
given bond dimension; and b) there exist local operators which, when applied
over any hMPS of a given bond dimension, decouple (cut) the particles where
they act from the spin chain while at the same time join (glue) the two loose
ends back again into a hMPS. Armed with these tools, we show how to
systematically derive `bond dimension witnesses', or 2-local operators whose
expectation value allows us to lower bound the bond dimension of the underlying
hMPS. We extend some of these results to the ansatz of Projected Entangled
Pairs States (PEPS). As a bonus, we use our insight on the structure of hMPS
to: a) derive some theoretical limitations on the use of hMPS and hPEPS for
ground state energy computations; b) show how to decrease the complexity and
boost the speed of convergence of the semidefinite programming hierarchies
described in [Phys. Rev. Lett. 115, 020501 (2015)] for the characterization of
finite-dimensional quantum correlations.Comment: Accepted for publication in Quantum. We still do not acknowledge
support from the European Research Counci
Combinatorial tangle Floer homology
In this paper we extend the idea of bordered Floer homology to knots and
links in : Using a specific Heegaard diagram, we construct gluable
combinatorial invariants of tangles in , and . The
special case of gives back a stabilized version of knot Floer homology.Comment: 106 pages, 44 figure
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