120 research outputs found
Total, elastic and diffractive cross sections at LHC in the Miettinen-Pumplin model
Predictions for the total, elastic and single diffractive cross sections
calculated for the LHC in the framework of the Miettinen-Pumplin model are
presented. The total cross section is expected to be 15% smaller than that
determined by Donnachie and Landshoff in the model with soft pomeron. The
diffractive cross section is almost constant in the Tevatron-LHC energy range.Comment: 8 pages, 5 figures, revised version to appear in Phys.Lett.
Saturation effects in forward-forward dijet production in p+Pb collisions
We study saturation effects in the production of forward dijets in
proton-lead collisions at the Large Hadron Collider, using the framework of
High Energy Factorization. Such configurations, with both jets produced in the
forward direction, probe the gluon density of the lead nucleus at small
longitudinal momentum fraction, and also limit the phase space for emissions of
additional jets. We find significant suppression of the forward dijet azimuthal
correlations in proton-lead versus proton-proton collisions, which we attribute
to stronger saturation of the gluon density in the nucleus than in the proton.
In order to minimize model dependence of our predictions, we use two different
extensions of the Balitsky-Kovchegov equation for evolution of the gluon
density with sub-leading corrections.Comment: 13 pages, 4 figures; v2: added figure 4, several clarifying sentences
and a reference; version accepted by PR
Improved TMD factorization for forward dijet production in dilute-dense hadronic collisions
We study forward dijet production in dilute-dense hadronic collisions. By
considering the appropriate limits, we show that both the
transverse-momentum-dependent (TMD) and the high-energy factorization formulas
can be derived from the Color Glass Condensate framework. Respectively, this
happens when the transverse momentum imbalance of the dijet system, , is
of the order of either the saturation scale, or the hard jet momenta, the
former being always much smaller than the latter. We propose a new formula for
forward dijets that encompasses both situations and is therefore applicable
regardless of the magnitude of . That involves generalizing the TMD
factorization formula for dijet production to the case where the incoming
small- gluon is off-shell. The derivation is performed in two independent
ways, using either Feynman diagram techniques, or color-ordered amplitudes.Comment: The improved version of the manuscript. 37 pages, 8 figures, several
table
Forward di-jet production in p+Pb collisions in the small-x improved TMD factorization framework
We study the production of forward di-jets in proton-lead and proton-proton
collisions at the Large Hadron Collider. Such configurations, with both jets
produced in the forward direction, impose a dilute-dense asymmetry which allows
to probe the gluon density of the lead or proton target at small longitudinal
momentum fractions. Even though the jet momenta are always much bigger than the
saturation scale of the target, , the transverse momentum imbalance of the
di-jet system may be either also much larger than , or of the order ,
implying that the small- QCD dynamics involved is either linear or
non-linear, respectively. The small- improved TMD factorization framework
deals with both situation in the same formalism. In the latter case, which
corresponds to nearly back-to-back jets, we find that saturation effects induce
a significant suppression of the forward di-jet azimuthal correlations in
proton-lead versus proton-proton collisions.Comment: 6 figure
Heavy flavour production in DGLAP improved saturation model
The charm and beauty quark production in deep inelastic scattering at low
values of the Bjorken variable x is considered in the DGLAP improved saturation
model. After fitting parameters of the model to the structure function F_2, the
heavy quark contributions Fc_2 and Fb_2 are predicted. A good description of
the data is found. Predictions for the longitudinal structure function F_L and
the diffractive structure function FD_2 are also presented.Comment: 16 pages, 7 figures; typos corrected, references added, final
Phys.Rev. D versio
A data-driven method of pile-up correction for the substructure of massive jets
We describe a method to measure and subtract the incoherent component of
energy flow arising from multiple interactions from jet shape/substructure
observables of ultra-massive jets. The amount subtracted is a function of the
jet shape variable of interest and not a universal property. Such a correction
is expected to significantly reduce any bias in the corresponding distributions
generated by the presence of multiple interactions, and to improve measurement
resolution. Since in our method the correction is obtained from the data, it is
not subject to uncertainties coming from the use of theoretical calculations
and/or Monte Carlo event generators. We derive our correction method for the
jet mass, angularity and planar flow. We find these corrections to be in good
agreement with data on massive jets observed by the CDF collaboration. Finally,
we comment on the linkage with the concept of jet area and jet mass area.Comment: 7 pages and 3 figures, minor correction
Dijet azimuthal correlations in p-p and p-Pb collisions at forward LHC calorimeters
We present a state-of-the-art computation for the production of forward
dijets in proton-proton and proton-lead collisions at the LHC, in rapidity
domains covered by the ATLAS calorimeter and the planned FoCal extension of the
ALICE detector. We use the small-x improved TMD (ITMD) formalism, together with
collinearly improved TMD gluon distributions and full b-space Sudakov
resummation, and discuss nonperturbative corrections due to hadronization and
showers using the Pythia event generator. We observe that forward dijets in
proton-nucleus collisions at moderately low pT are excellent probes of
saturation effects, as the Sudakov resummation does not alter the suppression
of the cross section.Comment: 14 page
Medium-modified average multiplicity and multiplicity fluctuations in jets
The energy evolution of average multiplicities and multiplicity fluctuations
in jets produced in heavy-ion collisions is investigated from a toy
QCD-inspired model. In this model, we use modified splitting functions
accounting for medium-enhanced radiation of gluons by a fast parton which
propagates through the quark gluon plasma. The leading contribution of the
standard production of soft hadrons is enhanced by a factor while
next-to-leading order (NLO) corrections are suppressed by , where
the parameter accounts for the induced-soft gluons in the medium. Our
results for such global observables are cross-checked and compared with their
limits in the vacuum.Comment: 8 pages and 4 figures. Version to be published in EPJ
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