15,270 research outputs found
Energy flow between jets in the kt algorithm
We consider the impact of the kt algorithm on energy flow into gaps between
jets in any QCD hard process. While we confirm the observation that the kt
clustering procedure considerably reduces the impact of non-global logarithms,
we unearth yet new sources of logarithmic enhancement, that stem from using the
algorithm to define the final state. We comment on the nature of the
logarithms we find and discuss their all-orders treatment.Comment: 4 pages, submitted to the proceedings of DIS 2006, Tsukuba, Japa
Phase Diagram of a Classical Fluid in a Quenched Random Potential
We consider the phase diagram of a classical fluid in the presence of a
random pinning potential of arbitrary strength. Introducing replicas for
averaging over the quenched disorder, we use the hypernetted chain
approximation to calculate the correlations in the replicated liquid. The
freezing transition of the liquid into a nearly crystalline state is studied
using a density functional approach, and the liquid-to-glass transition is
studied using a phenomenological replica symmetry breaking approach introduced
by Mezard and Parisi. The first-order liquid-to-crystal transition is found to
change to a continuous liquid-to-glass transition as the strength of the
disorder is increased above a threshold value.Comment: 7 pages, 4 figures, to appear in EuroPhysics Letter
Aspects of power corrections in hadron-hadron collisions
The program of understanding inverse-power law corrections to event shapes
and energy flow observables in e+ e- annihilation to two jets and DIS (1+1)
jets has been a significant success of QCD phenomenology over the last decade.
The important extension of this program to similar observables in hadron
collisions is not straightforward, being obscured by both conceptual and
technical issues. In this paper we shed light on some of these issues by
providing an estimate of power corrections to the inter-jet E_t flow
distribution in hadron collisions using the techniques that were employed in
the e+ e- annihilation and DIS cases.Comment: 15 pages, 1 figure, uses JHEP3.cl
Resummation of the jet broadening in DIS
We calculate the leading and next-to-leading logarithmic resummed
distribution for the jet broadening in deep inelastic scattering, as well as
the power correction for both the distribution and mean value. A truncation of
the answer at NLL accuracy, as is standard, leads to unphysical divergences. We
discuss their origin and show how the problem can be resolved. We then examine
DIS-specific procedures for matching to fixed-order calculations and compare
our results to data. One of the tools developed for the comparison is an NLO
parton distribution evolution code. When compared to PDF sets from MRST and
CTEQ it reveals limited discrepancies in both.Comment: 48 pages, 7 figure
The Qt distribution of the Breit current hemisphere in DIS as a probe of small-x broadening effects
We study the distribution 1/sigma dsigma/dQt, where Qt is the modulus of the
transverse momentum vector, obtained by summing over all hadrons, in the
current hemisphere of the DIS Breit frame. We resum the large logarithms in the
small Qt region, to next-to--leading logarithmic accuracy, including the
non-global logarithms involved. We point out that this observable is simply
related to the Drell-Yan vector boson and predicted Higgs Qt spectra at hadron
colliders. Comparing our predictions to existing HERA data thus ought to be a
valuable source of information on the role or absence of small-x (BFKL)
effects, neglected in conventional resummations of such quantities.Comment: 16 pages, 3 figures, uses JHEP3.cl
Problems in resumming interjet energy flows with k_t clustering
We consider the energy flow into gaps between hard jets. It was previously
believed that the accuracy of resummed predictions for such observables can be
improved by employing the clustering procedure to define the gap energy
in terms of a sum of energies of soft jets (rather than individual hadrons) in
the gap. This significantly reduces the sensitivity to correlated soft
large-angle radiation (non-global leading logs), numerically calculable only in
the large limit. While this is the case, as we demonstrate here, the use
of clustering spoils the straightforward single-gluon Sudakov
exponentiation that multiplies the non-global resummation. We carry out an
calculation of the leading single-logarithmic terms
and identify the piece that is omitted by straightforward exponentiation. We
compare our results with the full result from the
program EVENT2 to confirm our conclusions. For jets and DIS
(1+1) jets one can numerically resum these additional contributions as we show,
but for dijet photoproduction and hadron-hadron processes further studies are
needed.Comment: 11 pages, 5 figure
Fusion and breakup in the reactions of 6,7Li and 9Be
We develop a three body classical trajectory Monte Carlo (CTMC) method to
dicsuss the effect of the breakup process on heavy-ion fusion reactions induced
by weakly bound nuclei. This method follows the classical trajectories of
breakup fragments after the breakup takes place, and thus provides an
unambiguous separation between complete and incomplete fusion cross sections.
Applying this method to the fusion reaction Li + Bi, we find that
there is a significant contribution to the total complete fusion cross sections
from the process where all the breakup fragments are captured by the target
nucleus (i.e., the breakup followed by complete fusion).Comment: 4 pages, 3 eps figures. Uses espcrc1.sty. To be published in the
proceedings of the 8th international conference on clustering aspects of
nuclear structure and dynamics, November 24 - 29, 2003, Nara, Japan (Nucl.
Phys. A
Spatial persistence and survival probabilities for fluctuating interfaces
We report the results of numerical investigations of the steady-state (SS)
and finite-initial-conditions (FIC) spatial persistence and survival
probabilities for (1+1)--dimensional interfaces with dynamics governed by the
nonlinear Kardar--Parisi--Zhang (KPZ) equation and the linear
Edwards--Wilkinson (EW) equation with both white (uncorrelated) and colored
(spatially correlated) noise. We study the effects of a finite sampling
distance on the measured spatial persistence probability and show that both SS
and FIC persistence probabilities exhibit simple scaling behavior as a function
of the system size and the sampling distance. Analytical expressions for the
exponents associated with the power-law decay of SS and FIC spatial persistence
probabilities of the EW equation with power-law correlated noise are
established and numerically verified.Comment: 11 pages, 5 figure
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