1,742,054 research outputs found
Dispersive contributions to cross section ratio in forward regime
Two-photon exchange (TPE) contributions to elastic electron-proton scattering
in the forward regime are considered. The imaginary part of TPE amplitude in
these kinematics is related to the DIS nucleon structure functions. The real
part of the TPE amplitude is obtained from the imaginary part by means of
dispersion relations. We demonstrate that the dispersion integrals for the
relevant elastic -scattering amplitude converge and do not need
subtraction. This allows us to make clean prediction for the real part of the
TPE amplitude at forward angles. We furthermore compare and cross
sections which depends on the real part of TPE amplitude, and predict the
positron cross section to exceed the electron one by a few per cent, with the
difference ranging from 1.4% to 2.8% for electron energies in the range
from 3 to 45 GeV. We furthermore predict that the absolute value of this
asymmetry grows with energy, which makes it promising for experimental tests.Comment: 10 pages, 6 figure
The e p -> e' p eta reaction at and above the S11(1535) baryon resonance
New cross sections for the reaction e p -> ep eta are reported for total
center of mass energy W = 1.5--1.86 GeV and invariant momentum transfer Q^2 =
0.25--1.5 GeV^2. This large kinematic range allows extraction of important new
information about response functions, photocouplings, and eta N coupling
strengths of baryon resonances. Expanded W coverage shows sharp structure at W
\~ 1.7 GeV; this is shown to come from interference between S and P waves and
can be interpreted in terms of known resonances. Improved values are derived
for the photon coupling amplitude for the S11(1535) resonance.Comment: 11 pages, RevTeX, 5 figures, submitted to Phys. Rev. Let
AdS Bubbles, E-branes and Entanglement
The AdS-bubble solutions interestingly mimic Schr\"odinger-like geometries
when expressed in light-cone coordinates. These D bubble vacuas exhibit
asymmetric scaling property with a negative dynamical exponent of time ,
but are smooth geometries. Through a time-like T-duality we map these vacua to
E-brane bubbles with in type II* super-strings. We obtain an
expression for the entanglement entropy for `bubble E3-branes'. It is argued
that the entropy from E3-bubbles has to be the lowest.Comment: 15 pages, 1 figur
Risk factors for unfavourable postoperative outcome in patients with Crohn's disease undergoing right hemicolectomy or ileocaecal resection An international audit by ESCP and S-ECCO
Background
Patient and disease-related factors, as well as operation technique all have the potential to impact on postoperative outcome in Crohn's disease. The available evidence is based on small series and often displays conflicting results.
Aim
To investigate the effect of pre- and intra-operative risk factors on 30-day postoperative outcome in patients undergoing surgery for Crohn's disease.
Method
International prospective snapshot audit including consecutive patients undergoing right hemicolectomy or ileocaecal resection. This study analysed a subset of patients who underwent surgery for Crohn's disease. The primary outcome measure was the overall Clavien-Dindo postoperative complication rate. The key secondary outcomes were anastomotic leak, re-operation, surgical site infection and length of stay at hospital. Multivariable binary logistic regression analyses were used to produce odds ratios (OR) and 95% confidence intervals (CI).
Results
Three hundred and seventy five resections in 375 patients were included. The median age was 37 and 57.1% were female. In multivariate analyses, postoperative complications were associated with preoperative parenteral nutrition (OR 2.36 95% CI 1.10-4.97)], urgent/expedited surgical intervention (OR 2.00, 95% CI 1.13-3.55) and unplanned intraoperative adverse events (OR 2.30, 95% CI 1.20-4.45). The postoperative length of stay in hospital was prolonged in patients who received preoperative parenteral nutrition (OR 31, CI [1.08-1.61]) and those who had urgent/expedited operations (OR 1.21, CI [1.07-1.37]).
Conclusion
Preoperative parenteral nutritional support, urgent/expedited operation and unplanned intraoperative adverse events were associated with unfavourable postoperative outcome. Enhanced preoperative optimization and improved planning of operation pathways and timings may improve outcomes for patients
Triple collisions (e+p+Be7) in solar plasma
Several nuclear reactions involving the Be7 nucleus, not included into the
standard model of the pp-chain, are discussed. A qualitative analysis of their
possible influence on the fate of the Be7 in solar plasma and of their role in
the interpretation of the solar neutrino experiments is given. As an example,
the reaction rate of the nonradiative production of B8 in the triple collision
p + e^- + Be7 ---> B8 + e^- is estimated in the framework of the adiabatic
approximation. For the solar interior conditions the triple collision reaction
rate is approximately 10^{-4} of that for the binary process p + Be7 ---> B8 +
gamma .Comment: RevTeX, 15 pages, submitted to Nucl.Phys.
Maximal Abelian Subalgebras of e(p,q) algebras
Maximal abelian subalgebras of one of the classical real inhomogeneous Lie
algebras are constructed, namely those of the pseudoeuclidean Lie algebra
e(p,q). Use is made of the semidirect sum structure of e(p,q) with the
translations T(p+q) as an abelian ideal. We first construct splitting MASAs
that are themselves direct sums of abelian subalgebras of o(p,q) and of
subalgebras of T(p+q). The splitting subalgebras are used to construct the
complementary nonsplitting ones. We present general decomposition theorems and
construct indecomposable MASAs for all algebras e(p,q), p \geq q \geq 0. The
case of q=0 and 1 were treated earlier in a physical context. The case q=2 is
analyzed here in detail as an illustration of the general results.Comment: 29 pages, Late
Dilepton Production in and Colliders
In an collider, a striking signature for a dilepton gauge boson is
\ep \ ; this cross-section is calculated by using the helicity amplitude
technique. At HERA, with center-of-mass energy , a dilepton
mass above is inaccessible but at LEPII-LHC, with a center-of-mass
energy , masses up to 650 GeV can be discovered. In an
collider, the signature is \ee \ . The cross-sections of this process
are also calculated for the center-of-mass energies and
.Comment: 16 pages, 3 figures (not included), IFP-428-UN
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