353 research outputs found
Luminosity monitors at the LHC
We study the theoretical accuracy of various methods that have been proposed
to measure the luminosity of the LHC pp collider, as well as for Run II of the
Tevatron p barp collider. In particular we consider methods based on
(i) the total and forward elastic data, (ii) lepton-pair production and (iii)
W and Z production.Comment: 23 pages, Latex, 9 figure
Photoproduction of Quarkonium in Proton-Proton and Nucleus-Nucleus Collisions
We discuss the photoproduction of and at high energy
, and heavy ion colliders. We predict large rates in
interactions at the Fermilab Tevatron %and in heavy-ion interactions at the
CERN LHC. These reactions can be and in and heavy-ion interactions at the
CERN LHC. The is also produced copiously at RHIC. These reactions can
be used to study the gluon distribution in protons and heavy nuclei. We also
show that the different CP symmetries of the initial states lead to large
differences in the transverse momentum spectra of mesonsComment: 4 pgs. with 3 figure
Determination of the parameters of semiconducting CdF2:In with Schottky barriers from radio-frequency measurements
Physical properties of semiconducting CdF_2 crystals doped with In are
determined from measurements of the radio-frequency response of a sample with
Schottky barriers at frequencies 10 - 10^6 Hz. The dc conductivity, the
activation energy of the amphoteric impurity, and the total concentration of
the active In ions in CdF_2 are found through an equivalent-circuit analysis of
the frequency dependencies of the sample complex impedance at temperatures from
20 K to 300 K. Kinetic coefficients determining the thermally induced
transitions between the deep and the shallow states of the In impurity and the
barrier height between these states are obtained from the time-dependent
radio-frequency response after illumination of the material. The results on the
low-frequency conductivity in CdF_2:In are compared with submillimeter (10^{11}
- 10^{12} Hz) measurements and with room-temperature infrared measurements of
undoped CdF_2. The low-frequency impedance measurements of semiconductor
samples with Schottky barriers are shown to be a good tool for investigation of
the physical properties of semiconductors.Comment: 9 pages, 7 figure
Nonphotonic electrons at RHIC within -factorization approach and with experimental semileptonic decay functions
We discuss production of nonphotonic electrons in proton-proton scattering at
RHIC. The distributions in rapidity and transverse momentum of charm and bottom
quarks/antiquarks are calculated in the -factorization approach. We use
different unintegrated gluon distributions from the literature. The
hadronization of heavy quarks is done by means of Peterson and Braaten et al.
fragmentation functions. The semileptonic decay functions are found by fitting
recent semileptonic data obtained by the CLEO and BABAR collaborations. We get
good description of the data at large transverse momenta of electrons and find
a missing strength concentrated at small transverse momenta of electrons.
Plausible missing mechanisms are discussed.Comment: 16 pages, 11 figure
Forward Physics with Rapidity Gaps at the LHC
A rapidity gap program with great potential can be realized at the Large
Hadron Collider, LHC, by adding a few simple forward shower counters (FSCs)
along the beam line on both sides of the main central detectors, such as CMS.
Measurements of single diffractive cross sections down to the lowest masses can
be made with an efficient level-1 trigger. Exceptionally, the detectors also
make feasible the study of Central Diffractive Excitation, and in particular
the reaction g + g to g + g, in the color singlet channel, effectively using
the LHC as a gluon-gluon collider.Comment: 15 pages, 11 figure
Spin-dependent transport in p+-CdBxF2-x - n-CdF2 planar structures
The CV measurements and tunneling spectroscopy are used to study the
ballistic transport of the spin-polarized holes by varying the value of the
Rashba spin-orbit interaction (SOI) in the p-type quantum well prepared on the
surface of the n-CdF2 bulk crystal. The findings of the hole conductance
oscillations in the plane of the p-type quantum well that are due to the
variations of the Rashba SOI are shown to be evidence of the spin transistor
effect, with the amplitude of the oscillations close to e2/h.Comment: 5 pages, 6 figure
Consistent Treatment of Charm Evolution in Deep Inelastic Scattering
We present a formulation which allows heavy quark (c, b, ...) mass effects to
be explicitly incorporated in both the coefficient functions and the splitting
functions in the parton evolution equations. We obtain a consistent procedure
for evolution through the threshold regions for c anti-c and b anti-b
production in deep inelastic scattering, which allows the prediction of the
charm and bottom quark densities. We use the new formulation to perform a
next-to-leading order global parton analysis of deep inelastic and related hard
scattering data. We find that the optimum fit has alpha_S(M_Z^2) = 0.118. We
give predictions for the charm components of the proton structure functions F_2
and F_L as functions of x and Q^2 and, in particular, find that F_2^c is in
good agreement with the existing measurements. We examine the Q^2 range of
validity of the photon-gluon fusion model for c anti-c electroproduction. We
emphasize the value of a precision measurement of the charm component F_2^c at
HERA.Comment: 22 pages (latex), 9 postscript figures. In this revised version of
the paper we take a different choice of evolution scale. Rather than the
"physically natural" scale used in the original version of the paper, we now
choose the scale so that it reproduces the MSbar scheme for Q^2 >> m_c^2. The
global analysis of the data is repeated for this choice of evolution scal
Breakdown of Scaling in the Nonequilibrium Critical Dynamics of the Two-Dimensional XY Model
The approach to equilibrium, from a nonequilibrium initial state, in a system
at its critical point is usually described by a scaling theory with a single
growing length scale, , where z is the dynamic exponent
that governs the equilibrium dynamics. We show that, for the 2D XY model, the
rate of approach to equilibrium depends on the initial condition. In
particular, if no free vortices are present in the
initial state, while if free vortices are
present.Comment: 4 pages, 3 figure
Color Evaporation and Elastic Photoproduction at DESY HERA
The diffractive photoproduction of vector mesons is usually described
considering the two-gluon (Pomeron) exchange, non-diagonal parton distributions
and the contribution of the real part to the cross section. In this letter we
analyze the diffractive photoproduction of the at HERA using an
alternative model, the Color Evaporation Model (CEM), where the cross section
is simply determined by the boson-gluon cross section and an assumption for the
production of the colorless state. We verify that, similarly to the
case, the HERA data for this process can be well described by the CEM.
Moreover, we propose the analyzes of the ratio to discriminate between the distinct approaches.Comment: 7 pages, 3 figures, accepted for publication in PRD (Brief Reports
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