115 research outputs found
Hard diffractive quarkonium hadroproduction at high energies
We present a study of heavy quarkonium production in hard diffractive process
by the Pomeron exchange for Tevatron and LHC energies. The numerical results
are computed using recent experimental determination of the diffractive parton
density functions in Pomeron and are corrected by unitarity corrections through
gap survival probability factor. We give predictions for single as well as
central diffractive ratios. These processes are sensitive to the gluon content
of the Pomeron at small Bjorken-x and may be particularly useful in studying
the small-x physics. They may also be a good place to test the different
available mechanisms for quarkonium production at hadron colliders.Comment: 7 pages, 3 figures, 1 table. Final version to be published in
European Physical Journal
The ARGO-YBJ Experiment Progresses and Future Extension
Gamma ray source detection above 30TeV is an encouraging approach for finding
galactic cosmic ray origins. All sky survey for gamma ray sources using wide
field of view detector is essential for population accumulation for various
types of sources above 100GeV. To target the goals, the ARGO-YBJ experiment has
been established. Significant progresses have been made in the experiment. A
large air shower detector array in an area of 1km2 is proposed to boost the
sensitivity. Hybrid detection with multi-techniques will allow a good
discrimination between different types of primary particles, including photons
and protons, thus enable an energy spectrum measurement for individual specie.
Fluorescence light detector array will extend the spectrum measurement above
100PeV where the second knee is located. An energy scale determined by balloon
experiments at 10TeV will be propagated to ultra high energy cosmic ray
experiments
High Altitude test of RPCs for the ARGO-YBJ experiment
A 50 m**2 RPC carpet was operated at the YangBaJing Cosmic Ray Laboratory
(Tibet) located 4300 m a.s.l. The performance of RPCs in detecting Extensive
Air Showers was studied. Efficiency and time resolution measurements at the
pressure and temperature conditions typical of high mountain laboratories, are
reported.Comment: 16 pages, 10 figures, submitted to Nucl. Instr. Met
Quarkonium Physics at a Fixed-Target Experiment using the LHC Beams
We outline the many quarkonium-physics opportunities offered by a
multi-purpose fixed-target experiment using the p and Pb LHC beams extracted by
a bent crystal. This provides an integrated luminosity of 0.5 fb-1 per year on
a typical 1cm-long target. Such an extraction mode does not alter the
performance of the collider experiments at the LHC. With such a high
luminosity, one can analyse quarkonium production in great details in pp, pd
and pA collisions at sqrt(sNN)~115 GeV and at sqrt(sNN)~72 GeV in PbA
collisions. In a typical pp (pA) run, the obtained quarkonium yields per unit
of rapidity are 2-3 orders of magnitude larger than those expected at RHIC and
about respectively 10 (70) times larger than for ALICE. In PbA, they are
comparable. By instrumenting the target-rapidity region, the large negative-xF
domain can be accessed for the first time, greatly extending previous
measurements by Hera-B and E866. Such analyses should help resolving the
quarkonium-production controversies and clear the way for gluon PDF extraction
via quarkonium studies. The nuclear target-species versatility provides a
unique opportunity to study nuclear matter and the features of the hot and
dense matter formed in PbA collisions. A polarised proton target allows the
study of transverse-spin asymmetries in J/psi and Upsilon production, providing
access to the gluon and charm Sivers functions.Comment: Proceedings of the workshop "30 years of strong interactions", Spa,
Belgium, 6-8 April 2011. Version to appear in Few-Body Systems. 14 pages, 2
tables, LaTe
ARGO-YBJ constraints on very high energy emission from GRBs
The ARGO-YBJ (Astrophysical Radiation Ground-based Observatory at YangBaJing)
experiment is designed for very high energy -astronomy and cosmic ray
researches. Due to the full coverage of a large area () with
resistive plate chambers at a very high altitude (4300 m a.s.l.), the ARGO-YBJ
detector is used to search for transient phenomena, such as Gamma-ray bursts
(GRBs). Because the ARGO-YBJ detector has a large field of view (2 sr)
and is operated with a high duty cycle (90%), it is well suited for GRB
surveying and can be operated in searches for high energy GRBs following alarms
set by satellite-borne observations at lower energies. In this paper, the
sensitivity of the ARGO-YBJ detector for GRB detection is estimated. Upper
limits to fluence with 99% confidence level for 26 GRBs inside the field of
view from June 2006 to January 2009 are set in the two energy ranges 10100
GeV and 10 GeV1 TeV.Comment: accepted for publication in Astroparticle Physic
Gluons and the quark sea at high energies: distributions, polarization, tomography
This report is based on a ten-week program on "Gluons and the quark sea at
high-energies", which took place at the Institute for Nuclear Theory in Seattle
in Fall 2010. The principal aim of the program was to develop and sharpen the
science case for an Electron-Ion Collider (EIC), a facility that will be able
to collide electrons and positrons with polarized protons and with light to
heavy nuclei at high energies, offering unprecedented possibilities for
in-depth studies of quantum chromodynamics. This report is organized around
four major themes: i) the spin and flavor structure of the proton, ii)
three-dimensional structure of nucleons and nuclei in momentum and
configuration space, iii) QCD matter in nuclei, and iv) Electroweak physics and
the search for physics beyond the Standard Model. Beginning with an executive
summary, the report contains tables of key measurements, chapter overviews for
each of the major scientific themes, and detailed individual contributions on
various aspects of the scientific opportunities presented by an EIC.Comment: 547 pages, A report on the joint BNL/INT/Jlab program on the science
case for an Electron-Ion Collider, September 13 to November 19, 2010,
Institute for Nuclear Theory, Seattle; v2 with minor changes, matches printed
versio
Measurement of prompt hadron production ratios in collisions at 0.9 and 7 TeV
The charged-particle production ratios , , ,
, and are measured with the LHCb detector using of collisions delivered by the LHC at TeV and
at TeV. The measurements are performed as a
function of transverse momentum and pseudorapidity . The
production ratios are compared to the predictions of several Monte Carlo
generator settings, none of which are able to describe adequately all
observables. The ratio is also considered as a function of rapidity
loss, , and is used to constrain models of
baryon transport.Comment: Incorrect entries in Table 2 corrected. No consequences for rest of
pape
Multi-ancestry study of blood lipid levels identifies four loci interacting with physical activity
Many genetic loci affect circulating lipid levels, but it remains unknown whether lifestyle factors, such as physical activity, modify these genetic effects. To identify lipid loci interacting with physical activity, we performed genome-wide analyses of circulating HDL cholesterol, LDL cholesterol, and triglyceride levels in up to 120,979 individuals of European, African, Asian, Hispanic, and Brazilian ancestry, with follow-up of suggestive associations in an additional 131,012 individuals. We find four loci, in/near CLASP1, LHX1, SNTA1, and CNTNAP2, that are associated with circulating lipid levels through interaction with physical activity; higher levels of physical activity enhance the HDL cholesterol-increasing effects of the CLASP1, LHX1, and SNTA1 loci and attenuate the LDL cholesterol- increasing effect of the CNTNAP2 locus. The CLASP1, LHX1, and SNTA1 regions harbor genes linked to muscle function and lipid metabolism. Our results elucidate the role of physical activity interactions in the genetic contribution to blood lipid levels
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