85 research outputs found
From bubbles to foam: dilute to dense evolution of hadronic wave function at high energy
We derive the evolution of a hadronic light cone wave function with energy at
weak coupling. Our derivation is valid both in the high and the low partonic
density limit, and thus encompasses both the JIMWLK and the KLWMIJ evolution.
The hadronic wave function is shown to evolve by the action of the
Bogoliubov-type operator, which diagonalizes on the soft gluon sector the
light-cone hamiltonian in the presence of an arbitrary valence charge density.
We find explicitly the action of this operator on the soft as well as the
valence degrees of freedom of the theory.Comment: 30 page
Geometric scaling in exclusive processes
We show that according to the present understanding of the energy evolution
of the observables measured in deep-inelastic scattering, the photon-proton
scattering amplitude has to exhibit geometric scaling at each impact parameter.
We suggest a way to test it experimentally at HERA. A qualitative analysis
based on published data is presented and discussed.Comment: 9 pages, 2 figures. v2: references added, some points clarifie
Chiral Behaviour of the Rho Meson in Lattice QCD
In order to guide the extrapolation of the mass of the rho meson calculated
in lattice QCD with dynamical fermions, we study the contributions to its
self-energy which vary most rapidly as the quark mass approaches zero; from the
processes and . It turns out that in
analysing the most recent data from CP-PACS it is crucial to estimate the
self-energy from using the same grid of discrete momenta as
included implicitly in the lattice simulation. The correction associated with
the continuum, infinite volume limit can then be found by calculating the
corresponding integrals exactly. Our error analysis suggests that a factor of
10 improvement in statistics at the lowest quark mass for which data currently
exists would allow one to determine the physical rho mass to within 5%.
Finally, our analysis throws new light on a long-standing problem with the
J-parameter.Comment: 13 pages, 7 figures. Full analytic forms of the self-energies are
included and a correction in the omega-pi self-energ
Search for Chargino and Neutralino Production at sqrt(s) = 192-209 GeV at LEP
Approximately 438 pb-1 of e+e- data from the OPAL detector, taken with the
LEP collider running at centre-of-mass energies of 192-209 Gev, are analyzed to
search for evidence of chargino pair production, e+e- -> tilde chi^+_1 tilde
chi^-_1, or neutralino associated production, e+e- -> tilde chi^0_2 tilde
chi^0_1. Limits are set at the 95% confidence level on the product of the
cross-section for the process e+e- -> tilde chi^+_1 tilde chi^-_1 and its
branching ratios to topologies containing jets and missing energy, of jest with
a lepton and missing energy, and on the product of the cross-section for e+e-
-> tilde chi^0_2 tilde chi^0_1 and its branching ratio to jets. R-parity
conservation is assumed throughout this paper. When these results are
interpreted in the context of the Constrained Minimal Supersymmetric Standard
Model, limits are also set on the masses of the tilde chi^+-_1, tilde chi^0_1
and tilde chi^0_2, and regions of the parameter space of the model are ruled
out. Nearly model-independent limits are also set at the 95% confidence level
on sigma(e+e- -> tilde chi^+_1 tilde chi^-_1) with the assumption that each
chargino decays via a W boson, and on sigma(e+e- -> tilde chi^0_2 tilde
chi^0_1) with the tilde chi^0_2 assumed to decay via a Z^0.Comment: 33 pages, 13 figures, Submitted to Eur Phys J.
Geometric Scaling in Inclusive Charm Production
We show that the cross section for inclusive charm production exhibits
geometric scaling in a large range of photon virtualities. In the HERA
kinematic domain the saturation momentum stays below the hard
scale , implying charm production probing mostly the color
transparency regime and unitarization effects being almost negligible. We
derive our results considering two saturation models which are able to describe
the DESY ep collider HERA data for the proton structure function at small
values of the Bjorken variable . A striking feature is the scaling on
above saturation limit, corroborating recent
theoretical studies.Comment: 4 pages, 2 figures. Version to be published in Physical Review
Letter
A model of decay
We suggest a parameterization of the matrix element for decay using kinematic variables convenient for experimental
analysis. The contributions of intermediate - and -states up
to spin 3 have been taken into account. The angular distributions for each
discussed hypothesis have been obtained and analysed using Monte-Carlo
simulation.Comment: 24 pages, 9 figures, 1 table; V2: text in some places improved and
acknowledgments adde
Shock waves in strongly coupled plasmas
Shock waves are supersonic disturbances propagating in a fluid and giving
rise to dissipation and drag. Weak shocks, i.e., those of small amplitude, can
be well described within the hydrodynamic approximation. On the other hand,
strong shocks are discontinuous within hydrodynamics and therefore probe the
microscopics of the theory. In this paper we consider the case of the strongly
coupled N=4 plasma whose microscopic description, applicable for scales smaller
than the inverse temperature, is given in terms of gravity in an asymptotically
space. In the gravity approximation, weak and strong shocks should be
described by smooth metrics with no discontinuities. For weak shocks we find
the dual metric in a derivative expansion and for strong shocks we use
linearized gravity to find the exponential tail that determines the width of
the shock. In particular we find that, when the velocity of the fluid relative
to the shock approaches the speed of light the penetration depth
scales as . We compare the results with second
order hydrodynamics and the Israel-Stewart approximation. Although they all
agree in the hydrodynamic regime of weak shocks, we show that there is not even
qualitative agreement for strong shocks. For the gravity side, the existence of
shock waves implies that there are disturbances of constant shape propagating
on the horizon of the dual black holes.Comment: 47 pages, 8 figures; v2:typos corrected, references adde
Stroke-prone salt-sensitive spontaneously hypertensive rats show higher susceptibility to spreading depolarization (SD) and altered hemodynamic responses to SD
Spreading depolarization (SD) occurs in a plethora of clinical conditions including migraine aura, delayed ischemia after subarachnoid hemorrhage and malignant hemispheric stroke. It describes waves of near-breakdown of ion homeostasis, particularly Na(+) homeostasis in brain gray matter. SD induces tone alterations in resistance vessels, causing either hyperperfusion in healthy tissue; or hypoperfusion (inverse hemodynamic response = spreading ischemia) in tissue at risk. Observations from mice with genetic dysfunction of the ATP1A2-encoded α(2)-isoform of Na(+)/K(+)-ATPase (α(2)NaKA) suggest a mechanistic link between (1) SD, (2) vascular dysfunction, and (3) salt-sensitive hypertension via α(2)NaKA. Thus, α(2)NaKA-dysfunctional mice are more susceptible to SD and show a shift toward more inverse hemodynamic responses. α(2)NaKA-dysfunctional patients suffer from familial hemiplegic migraine type 2, a Mendelian model disease of SD. α(2)NaKA-dysfunctional mice are also a genetic model of salt-sensitive hypertension. To determine whether SD thresholds and hemodynamic responses are also altered in other genetic models of salt-sensitive hypertension, we examined these variables in stroke-prone spontaneously hypertensive rats (SHRsp). Compared with Wistar Kyoto control rats, we found in SHRsp that electrical SD threshold was significantly reduced, propagation speed was increased, and inverse hemodynamic responses were prolonged. These results may have relevance to both migraine with aura and stroke
QCD Saturation in the Semi-classical Approach
In this paper the semi-classical approach to the solution of non-linear
evolution equation is developed. We found the solution in the entire kinematic
region to the non-linear evolution equation that governs the dynamics in the
high parton density QCD. The large impact parameter () behavior of the
solution is discussed as well as the way how to include the non-perturbative
QCD corrections in this region of . The geometrical scaling behavior and
other properties of the solution in the saturation (Color Glass Condensate)
kinematic domain are analyzed. We obtain the asymptotic behavior for the
physical observables and found the unitarity bounds for them.Comment: 41 pp. 19 figures in eps file
Chiral Magnetic Effect in Hydrodynamic Approximation
We review derivations of the chiral magnetic effect (ChME) in hydrodynamic
approximation. The reader is assumed to be familiar with the basics of the
effect. The main challenge now is to account for the strong interactions
between the constituents of the fluid. The main result is that the ChME is not
renormalized: in the hydrodynamic approximation it remains the same as for
non-interacting chiral fermions moving in an external magnetic field. The key
ingredients in the proof are general laws of thermodynamics and the
Adler-Bardeen theorem for the chiral anomaly in external electromagnetic
fields. The chiral magnetic effect in hydrodynamics represents a macroscopic
manifestation of a quantum phenomenon (chiral anomaly). Moreover, one can argue
that the current induced by the magnetic field is dissipation free and talk
about a kind of "chiral superconductivity". More precise description is a
ballistic transport along magnetic field taking place in equilibrium and in
absence of a driving force. The basic limitation is exact chiral limit while
the temperature--excitingly enough- does not seemingly matter. What is still
lacking, is a detailed quantum microscopic picture for the ChME in
hydrodynamics. Probably, the chiral currents propagate through
lower-dimensional defects, like vortices in superfluid. In case of superfluid,
the prediction for the chiral magnetic effect remains unmodified although the
emerging dynamical picture differs from the standard one.Comment: 35 pages, prepared for a volume of the Springer Lecture Notes in
Physics "Strongly interacting matter in magnetic fields" edited by D.
Kharzeev, K. Landsteiner, A. Schmitt, H.-U. Ye
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