1,028 research outputs found
Central exclusive production of longlived gluinos at the LHC
We examine the possibility of producing gluino pairs at the LHC via the
exclusive reaction pp -> p+gluino+gluino+p in the case where the gluinos are
long lived. Such long lived gluinos are possible if the scalar super-partners
have large enough masses. We show that it may be possible to observe the
gluinos via their conversion to R-hadron jets and measure their mass to better
than 1% accuracy for masses below 350 GeV with 300/fb of data.Comment: 13 pages, 9 figures. Minor corrections to version
Interpretation of the Flavor Dependence of Nucleon Form Factors in a Generalized Parton Distribution Model
We give an interpretation of the and quarks contributions to the
nucleon electromagnetic form factors for values of the four-momentum transfer
in the multi-GeV region where flavor separated data have been recently made
available. The data show, in particular, a suppression of quarks with
respect to quarks at large momentum transfer. %and constant ratios of the
flavor dependent Pauli to Dirac form factors ratios. This trend can be
explained using a reggeized diquark model calculation of generalized parton
distributions, thus providing a correlation between momentum and coordinate
spaces, both of which are necessary in order to interpret the partonic
substructure of the form factors. We extend our discussion to the second
moments of generalized parton distributions which are believed to contribute to
partonic angular momentum.Comment: 22 pages, 19 figures; results and figures added and changed, tables
added, formulae added, major rewriting of tex
Training in oesophageal surgery – The gold standard: A prospective study
AbstractIntroductionCompetency in complex oesophagogastric surgery, within the current climate of changes to medical training and reduced hours, requires repeated, focused, hands-on training. We describe the training methods for oesophagectomy in our institution.MethodsAll oesophageal resections under the care of one consultant surgeon are regarded as training cases. When trainees start they are shown the first resection; subsequently, the trainees then perform every case with the consultant scrubbed. Consultant input consists of retraction and tips in difficult situations. All data were collected on a prospective database.ResultsTwo hundered and seventy patients (215 males, median age=64 years) underwent primary oesophagectomy under the consultant, between January 2000 and May 2007. Fifteen resections (6%) were performed solely by the consultant. ASA grading was: I=15, II=154, III=95, IV=5, and unrecorded=1. In-hospital mortality and clinically apparent leak rate was 1.9% (5 deaths) and 6.2% (n=17), respectively. Reoperation was required in 15 patients (5.5%). The median length of hospital stay was 14 days (range=8–95 days). Median lymph node yield was 13 (range=0–64).ConclusionsTrainees under supervision can competently perform an oesophagectomy without compromising patient care. An early hands-on approach leads to a rapid ascent of the learning curve and is essential in today's climate of limited training opportunity
Properties of the BFKL equation and structure function predictions for HERA
The general properties of the Lipatov or BFKL equation are reviewed.
Modifications to the infrared region are proposed. Numerical predictions for
the deep-inelastic electron-proton structure functions at small are
presented and confronted with recent HERA measurements.Comment: 21 pages, 11 figures, Latex file, Durham preprint DTP 92/2
Test beam measurement of the first prototype of the fast silicon pixel monolithic detector for the TT-PET project
The TT-PET collaboration is developing a PET scanner for small animals with
30 ps time-of-flight resolution and sub-millimetre 3D detection granularity.
The sensitive element of the scanner is a monolithic silicon pixel detector
based on state-of-the-art SiGe BiCMOS technology. The first ASIC prototype for
the TT-PET was produced and tested in the laboratory and with minimum ionizing
particles. The electronics exhibit an equivalent noise charge below 600 e- RMS
and a pulse rise time of less than 2 ns, in accordance with the simulations.
The pixels with a capacitance of 0.8 pF were measured to have a detection
efficiency greater than 99% and, although in the absence of the
post-processing, a time resolution of approximately 200 ps
Proceedings of the workshop "Standard Model at the LHC" University College London 30 March - 1 April 2009
Proceedings from a 3-day discussion on Standard Model discoveries with the
first LHC dataComment: 9 contributions to the proceedings of the LHC Standard Model worksho
Reinstating the 'no-lose' theorem for NMSSM Higgs discovery at the LHC
The simplest supersymmetric model that solves the mu problem and in which the
GUT-scale parameters need not be finely tuned in order to predict the correct
value of the Z boson mass at low scales is the Next-to-Minimal Supersymmetric
Standard Model (NMSSM). However, in order that fine tuning be absent, the
lightest CP-even Higgs boson h should have mass ~100 GeV and SM couplings to
gauge bosons and fermions. The only way that this can be consistent with LEP
limits is if h decays primarily via h->aa->4 tau or 4j but not 4b, where a is
the lighter of the two pseudo-scalar Higgses that are present in the NMSSM.
Interestingly, m_a 2 m_tau somewhat
preferred. Thus, h -> 4 tau becomes a key mode of interest. Meanwhile, all
other Higgs bosons of the NMSSM are typically quite heavy. Detection of any of
the NMSSM Higgs bosons at the LHC in this preferred scenario will be very
challenging using conventional channels. In this paper, we demonstrate that the
h -> aa -> 4 tau decay chain should be visible if the Higgs is produced in the
process pp -> p+h+p with the final state protons being measured using suitably
installed forward detectors. Moreover, we show that the mass of both the h and
the a can be determined on an event-by-event basis.Comment: 23 page
Testing the dynamics of high energy scattering using vector meson production
I review work on diffractive vector meson production in photon-proton
collisions at high energy and large momentum transfer, accompanied by proton
dissociation and a large rapidity gap. This process provides a test of the high
energy scattering dynamics, but is also sensitive to the details of the
treatment of the vector meson vertex.
The emphasis is on the description of the process by a solution of the
non-forward BFKL equation, i.e. the equation describing the evolution of
scattering amplitudes in the high-energy limit of QCD. The formation of the
vector meson and the non-perturbative modeling needed is also briefly
discussed.Comment: 17 pages, 8 figures. Brief review to appear in Mod. Phys. Lett.
Deep inelastic scattering and "elastic" diffraction
We examine the total cross section of virtual photons on protons,
, at low and its
connection with ``elastic'' diffractive production in the two-gluon exchange dynamics for the virtual forward
Compton scattering amplitude. Solely based on the generic structure of
two-gluon exchange, we establish that the cross section is described by the
(imaginary part of the) amplitude for forward scattering of vector
states, . The
generalized vector dominance/color dipole picture (GVD/CDP) is accordingly
established to only rest on the two-gluon-exchange generic structure. This is
explicitly seen by the sum rules that allow one to directly relate the total
cross section to the cross section for elastic diffractive forward production,
, of vector states.Comment: 24 pages, latex file with three eps figures. BI-TP 2002/2
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