2,255 research outputs found
Gluon distribution in proton at soft and hard pp collisions
We analyze the inclusive spectra of hadrons produced in collisions at
high energies in the mid-rapidity region within the soft QCD and perturbative
QCD assuming the possible creation of the soft gluons at low intrinsic
transverse momenta . From the best description of the LHC data we found
the parametrization of the unintegrated gluon distribution which at low
is different from the one obtained within the perturbative QCD.Comment: 10 pages, 5 figures. Talk given the 5th joint International HADRON
STRUCTURE '11 Conference (HS'11), Tatransk\'a Strba, Slovakia, June 27th -
July 1st, 201
Indecomposability parameters in chiral Logarithmic Conformal Field Theory
Work of the last few years has shown that the key algebraic features of
Logarithmic Conformal Field Theories (LCFTs) are already present in some finite
lattice systems (such as the XXZ spin-1/2 chain) before the continuum limit is
taken. This has provided a very convenient way to analyze the structure of
indecomposable Virasoro modules and to obtain fusion rules for a variety of
models such as (boundary) percolation etc. LCFTs allow for additional quantum
numbers describing the fine structure of the indecomposable modules, and
generalizing the `b-number' introduced initially by Gurarie for the c=0 case.
The determination of these indecomposability parameters has given rise to a lot
of algebraic work, but their physical meaning has remained somewhat elusive. In
a recent paper, a way to measure b for boundary percolation and polymers was
proposed. We generalize this work here by devising a general strategy to
compute matrix elements of Virasoro generators from the numerical analysis of
lattice models and their continuum limit. The method is applied to XXZ spin-1/2
and spin-1 chains with open (free) boundary conditions. They are related to
gl(n+m|m) and osp(n+2m|2m)-invariant superspin chains and to nonlinear sigma
models with supercoset target spaces. These models can also be formulated in
terms of dense and dilute loop gas. We check the method in many cases where the
results were already known analytically. Furthermore, we also confront our
findings with a construction generalizing Gurarie's, where logarithms emerge
naturally in operator product expansions to compensate for apparently divergent
terms. This argument actually allows us to compute indecomposability parameters
in any logarithmic theory. A central result of our study is the construction of
a Kac table for the indecomposability parameters of the logarithmic minimal
models LM(1,p) and LM(p,p+1).Comment: 32 pages, 2 figures, Published Versio
Description of LHC data in a soft interaction model
We show in this paper that we have found a set of parameters in our model for
the soft interactions at high energy, that successfully describes all high
energy experimental data, including the LHC data.
This model is based on a single Pomeron with large intercept \Delta_\pom =
0.23 and slope \alpha'_\pom = 0, that describes both long and short distance
processes. It also provides a natural matching with perturbative QCD. All
features of our model are similar to the expectations of N=4 SYM, which at
present is the only theory that is able to treat srong interactions on a
theoretical basis.Comment: 11 pages with 7 figures in eps format
Leading indicators of fiscal distress: evidence from extreme bounds analysis
Early warning systems (EWSs) are widely used to assess a country’s vulnerability to fiscal distress. A fiscal distress episode is identified as a period when government experiences extreme funding difficulties. Most EWSs employ a specific set of only fiscal leading indicators predetermined by the researchers, which casts doubt on their robustness. We revisit this issue using extreme bounds analysis, which allows identifying robust leading indicators of fiscal distress from a large set. A robust leading indicator’s effect does not strongly depend on the model specification. Consistent with the theoretical predictions of latest generation crisis models, we find that both fiscal and non-fiscal leading indicators are robust. In addition, we find that a fiscal vulnerability indicator based on fiscal and non-fiscal leading indicators offers a 29% gain in predictive power compared to a traditional one based only on fiscal leading indicators. This suggests that both fiscal and non-fiscal leading indicators should be taken into account when assessing country’s vulnerability to fiscal distress
On the rise of proton-proton cross-sections at high energies
The rise of the total, elastic and inelastic hadronic cross sections at high
energies is investigated by means of an analytical parametrization, with the
exponent of the leading logarithm contribution as a free fit parameter. Using
derivative dispersion relations with one subtraction, two different fits to
proton-proton and antiproton-proton total cross section and rho parameter data
are developed, reproducing well the experimental information in the energy
region 5 GeV - 7 TeV. The parametrization for the total cross sections is then
extended to fit the elastic (integrated) cross section data in the same energy
region, with satisfactory results. From these empirical results we extract the
energy dependence of several physical quantities: inelastic cross section,
ratios elastic/total, inelastic/total cross sections, ratio
total-cross-section/elastic-slope, elastic slope and optical point. All data,
fitted and predicted, are quite well described. We find a statistically
consistent solution indicating: (1) an increase of the hadronic cross sections
with the energy faster than the log-squared bound by Froissart and Martin; (2)
asymptotic limits 1/3 and 2/3 for the ratios elastic/total and inelastic/total
cross sections, respectively, a result in agreement with unitarity. These
indications corroborate recent theoretical arguments by Ya. I. Azimov on the
rise of the total cross section.Comment: 35 pages, 12 figures, discussions improved with further
clarifications, references added and updated, one note added, results and
conclusions unchanged. Version to be published in J. Phys. G: Nucl. Part.
Phy
Kazhdan-Lusztig equivalence and fusion of Kac modules in Virasoro logarithmic models
The subject of our study is the Kazhdan-Lusztig (KL) equivalence in the
context of a one-parameter family of logarithmic CFTs based on Virasoro
symmetry with the (1,p) central charge. All finite-dimensional indecomposable
modules of the KL-dual quantum group - the "full" Lusztig quantum sl(2) at the
root of unity - are explicitly described. These are exhausted by projective
modules and four series of modules that have a functorial correspondence with
any quotient or a submodule of Feigin-Fuchs modules over the Virasoro algebra.
Our main result includes calculation of tensor products of any pair of the
indecomposable modules. Based on the Kazhdan-Lusztig equivalence between
quantum groups and vertex-operator algebras, fusion rules of Kac modules over
the Virasoro algebra in the (1,p) LCFT models are conjectured.Comment: 40pp. V2: a new introduction, corrected typos, some explanatory
comments added, references adde
Proton-proton cross-sections: the interplay between density and radius
We argue that there are two mechanisms responsable for the growth of high
energy cross-sections - \sigma_{tot} and \sigma_{el}, say - in pp collisions.
One is by the increase of matter \emph{density}, resulting in the black disk
saturation. The other is by exclusively radial expansion affecting the
periphery of the overlap area. Within this simple model we can reproduce all
available data in pp from ISR to LHC. In order to achieve a fast growth in the
very high energy cosmic ray energies, we propose a fast black disk saturation
followed by the dominance of geometric scaling (GS)
Jet energy measurement with the ATLAS detector in proton-proton collisions at root s=7 TeV
The jet energy scale and its systematic uncertainty are determined for jets measured with the ATLAS detector at the LHC in proton-proton collision data at a centre-of-mass energy of √s = 7TeV corresponding to an integrated luminosity of 38 pb-1. Jets are reconstructed with the anti-kt algorithm with distance parameters R=0. 4 or R=0. 6. Jet energy and angle corrections are determined from Monte Carlo simulations to calibrate jets with transverse momenta pT≥20 GeV and pseudorapidities {pipe}η{pipe}<4. 5. The jet energy systematic uncertainty is estimated using the single isolated hadron response measured in situ and in test-beams, exploiting the transverse momentum balance between central and forward jets in events with dijet topologies and studying systematic variations in Monte Carlo simulations. The jet energy uncertainty is less than 2. 5 % in the central calorimeter region ({pipe}η{pipe}<0. 8) for jets with 60≤pT<800 GeV, and is maximally 14 % for pT<30 GeV in the most forward region 3. 2≤{pipe}η{pipe}<4. 5. The jet energy is validated for jet transverse momenta up to 1 TeV to the level of a few percent using several in situ techniques by comparing a well-known reference such as the recoiling photon pT, the sum of the transverse momenta of tracks associated to the jet, or a system of low-pT jets recoiling against a high-pT jet. More sophisticated jet calibration schemes are presented based on calorimeter cell energy density weighting or hadronic properties of jets, aiming for an improved jet energy resolution and a reduced flavour dependence of the jet response. The systematic uncertainty of the jet energy determined from a combination of in situ techniques is consistent with the one derived from single hadron response measurements over a wide kinematic range. The nominal corrections and uncertainties are derived for isolated jets in an inclusive sample of high-pT jets. Special cases such as event topologies with close-by jets, or selections of samples with an enhanced content of jets originating from light quarks, heavy quarks or gluons are also discussed and the corresponding uncertainties are determined. © 2013 CERN for the benefit of the ATLAS collaboration
Multiplicity dependence of jet-like two-particle correlations in p-Pb collisions at = 5.02 TeV
Two-particle angular correlations between unidentified charged trigger and
associated particles are measured by the ALICE detector in p-Pb collisions at a
nucleon-nucleon centre-of-mass energy of 5.02 TeV. The transverse-momentum
range 0.7 5.0 GeV/ is examined,
to include correlations induced by jets originating from low
momen\-tum-transfer scatterings (minijets). The correlations expressed as
associated yield per trigger particle are obtained in the pseudorapidity range
. The near-side long-range pseudorapidity correlations observed in
high-multiplicity p-Pb collisions are subtracted from both near-side
short-range and away-side correlations in order to remove the non-jet-like
components. The yields in the jet-like peaks are found to be invariant with
event multiplicity with the exception of events with low multiplicity. This
invariance is consistent with the particles being produced via the incoherent
fragmentation of multiple parton--parton scatterings, while the yield related
to the previously observed ridge structures is not jet-related. The number of
uncorrelated sources of particle production is found to increase linearly with
multiplicity, suggesting no saturation of the number of multi-parton
interactions even in the highest multiplicity p-Pb collisions. Further, the
number scales in the intermediate multiplicity region with the number of binary
nucleon-nucleon collisions estimated with a Glauber Monte-Carlo simulation.Comment: 23 pages, 6 captioned figures, 1 table, authors from page 17,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/161
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