1,288 research outputs found
Forward Physics at the LHC: within and beyond the Standard Model
We review the detection capabilities in the forward direction of the various
LHC experiments together with the associated physics programme. A selection of
measurements accessible with near-beam instrumentation in various sectors (and
extensions) of the Standard Model (SM) is outlined, including QCD (diffractive
and elastic scattering, low-x parton dynamics, hadronic Monte Carlos for
cosmic-rays), electroweak processes in gamma-gamma interactions, and Higgs
physics (vector-boson-fusion and central exclusive production).Comment: 9 pages, 18 figs. Lectures given at the LAWHEP'07 School (Sao Miguel
das Missoes, Brazil, 3-7 Dec 2007) to appear in Braz. J. Phys. Also presented
in HLPW08 (Spa, Belgium, 6-8 Mar 2008) AIP Conf. Proceeds, to appear; and in
HANUC European Grad. School (Jyvaskyla, Finland, 25-29 Aug. 2008
Single inclusive pion pT-spectra in proton-proton collisions at sqrt(s) = 22.4GeV: data versus perturbative QCD calculations
We compare the inclusive transverse momentum spectra of single pions above pT
= 3 GeV/c measured in proton-proton (p-p) collisions at sqrt(s) = 21.7 - 23.8
GeV, with next-to-leading order (NLO) perturbative QCD (pQCD) predictions using
recent parametrizations of the parton densities and parton-to-pion
fragmentation functions. Although the dependence on the theoretical scales is
large, the calculations can reproduce the experimental results both in
magnitude and shape. Based on the existing data and on a pQCD
-rescaling of the measured spectra, we provide a practical
parametrization of the baseline p-p pion transverse momentum spectrum to be
compared to nucleus-nucleus collisions data at sqrt(s_NN) = 22.4 GeV.Comment: 16 pages, 7 figure
Low-x QCD studies with forward jets in proton-proton collisions at sqrt{s} = 14 TeV in CMS
Forward (di)jet measurements are a useful tool to constrain the Parton
Distribution Functions (PDFs) at low values of parton momentum fraction x, and
to study the possible onset of BFKL or gluon saturation QCD evolutions in the
proton. We present studies of jet reconstruction capabilities in the CMS Hadron
Forward (HF) calorimeter (3<|eta|<5). The expected sensitivity of the inclusive
forward jet p_T spectrum to the proton PDF, as well as the azimuthal
decorrelation of Mueller-Navelet jets with a large rapidity separation are
presented for p-p collisions at sqrt{s} = 14 TeV.Comment: 5 pages, 8 figures. Proceedings Diffraction 2008: International
Workshop on Diffraction in High Energy Physics, La Londe-les-Maures, France,
9-14 Sep 200
Single-inclusive production of large-pT charged particles in hadronic collisions at TeV energies and perturbative QCD predictions
The single inclusive spectrum of charged particles with transverse momenta
pT=3-150 GeV/c measured at midrapidity by the CDF experiment in
proton-antiproton (p-pbar) collisions at sqrt(s)=1.96 TeV is compared to
next-to-leading order (NLO) perturbative QCD calculations using the most recent
parametrizations of the parton distributions and parton-to-hadron fragmentation
functions. Above pT~20 GeV/c, there is a very sizeable disagreement of the
Tevatron data compared to the NLO predictions and to xT-scaling expectations,
suggesting a problem in the experimental data. We also present the predictions
for the pT-differential charged hadron spectra and the associated theoretical
uncertainties for proton-proton (p-p) collisions at LHC energies
(sqrt(s)=0.9-14 TeV). Two procedures to estimate the charged hadron spectra at
LHC heavy-ion collision energies (sqrt(s)=2.76,5.5 TeV) from p-p measurements
are suggested.Comment: 23 pages, 9 figures. A few text additions. Accepted for publication
in JHE
Study of Higgs boson production and its b-bbar decay in gamma-gamma processes in proton-nucleus collisions at the LHC
We explore for the first time the possibilities to measure an
intermediate-mass (mH = 115-140 GeV/c^2) Standard-Model Higgs boson in
electromagnetic proton-lead (pPb) interactions at the CERN Large Hadron
Collider (LHC) via its b-bbar decay. Using equivalent Weizsaecker-Williams
photon fluxes and Higgs effective field theory for the coupling gamma-gamma -->
H, we obtain a leading-order cross section of the order of 0.3 pb for exclusive
Higgs production in elastic (pPb --> gamma-gamma --> p H Pb) and semielastic
(pPb --> gamma-gamma --> Pb H X) processes at sqrt(s) = 8.8 TeV. After applying
various kinematics cuts to remove the main backgrounds (gamma-gamma --> b-bbar
and misidentified gamma-gamma-->q-qbar events), we find that a Higgs boson with
mH = 120 GeV/c^2 could be observed in the b-bbar channel with a
3sigma-significance integrating 300 pb^-1 with an upgraded pA luminosity of
10^31 cm^-2s^-1. We also provide for the first time semielastic Higgs cross
sections, along with elastic t-tbar cross sections, for electromagnetic pp, pA
and AA collisions at the LHC.Comment: 22 pages, 8 figures. Tiny changes. Version as publishe
The strong interaction at the collider and cosmic-rays frontiers
First data on inclusive particle production measured in proton-proton
collisions at the Large Hadron Collider (LHC) are compared to predictions of
various hadron-interaction Monte Carlos (QGSJET, EPOS and SIBYLL) used commonly
in high-energy cosmic-ray physics. While reasonable overall agreement is found
for some of the models, none of them reproduces consistently the sqrt(s)
evolution of all the measured observables. We discuss the implications of the
new LHC data for the modeling of the non-perturbative and semihard parton
dynamics in hadron-hadron and cosmic-rays interactions at the highest energies
studied today.Comment: 7 pages, Proceeds. Workshop "30 years of strong interactions", Spa,
Belgium, 6-8 April 2011. Elsevier to appea
Jet Tomography in the Forward Direction at RHIC
Hadron production at high- displays a strong suppression pattern in a
wide rapidity region in heavy ion collisions at RHIC energies. This finding
indicates the presence of strong final state effects for both transversally and
longitudinally traveling partons, namely induced energy loss. We have developed
a perturbative QCD based model to describe hadron production in collision,
which can be combined with the Glauber -- Gribov model to describe hadron
production in heavy ion collisions. Investigating and collisions
at energy GeV at mid-rapidity, we find the opacity of the
strongly interacting hot matter to be proportional to the participant nucleon
number. Considering forward rapidities, the suppression pattern indicates the
formation of a longitudinally contracted dense deconfined zone in central heavy
ion collisions. We determine parameters for the initial geometry from the
existing data.Comment: 6 pages for Hot Quarks '06 Conferenc
Constraints from the first LHC data on hadronic event generators for ultra-high energy cosmic-ray physics
The determination of the primary energy and mass of ultra-high-energy
cosmic-rays (UHECR) generating extensive air-showers in the Earth's atmosphere,
relies on the detailed modeling of hadronic multiparticle production at
center-of-mass (c.m.) collision energies up to two orders of magnitude higher
than those studied at particle colliders. The first Large Hadron Collider (LHC)
data have extended by more than a factor of three the c.m. energies in which we
have direct proton-proton measurements available to compare to hadronic models.
In this work we compare LHC results on inclusive particle production at
energies sqrt(s) = 0.9, 2.36, and 7 TeV to predictions of various hadronic
Monte Carlo (MC) models used commonly in cosmic-ray (CR) physics (QGSJET, EPOS
and SIBYLL). As a benchmark with a standard collider physics model we also show
PYTHIA (and PHOJET) predictions with various parameter settings. While
reasonable overall agreement is found for some of the MC, none of them
reproduces consistently the sqrt(s) evolution of all the observables. We
discuss implications of the new LHC data for the description of cosmic-ray
interactions at the highest energies.Comment: 25 pages, 12 figures. Minor mods. Matches version to appear in
Astroparticle Physic
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