232 research outputs found
Soft-gluon resummation for pseudoscalar Higgs boson production at hadron colliders
We compute the threshold-resummed cross section for pseudo-scalar MSSM Higgs
boson production by gluon fusion at hadron colliders. The calculation is
performed at next-to-next-to leading logarithmic accuracy. We present results
for both the LHC and Tevatron Run II. We analyze the factorization and
renormalization scale dependence of the results, finding that after performing
the resummation the corresponding cross section can be computed with an
accuracy better than 10%.Comment: 10 pages, 7 figures, accepted by Physics Letters
The structure of large logarithmic corrections at small transverse momentum in hadronic collisions
We consider the region of small transverse momenta in the production of
high-mass systems in hadronic collisions. By using the current knowledge on the
infrared behaviour of tree-level and one-loop QCD amplitudes at O(alpha_s^2),
we analytically compute the general form of the logarithmically-enhanced
contributions up to next-to-next-to-leading logarithmic accuracy. By comparing
the results with q_T-resummation formulae we extract the coefficients that
control the resummation of the large logarithmic contributions for both quark
and gluon channels. Our results show that within the conventional resummation
formalism the Sudakov form factor is actually process-dependent.Comment: 38 pages, 2 figures include
Constraining Dark Matter in the MSSM at the LHC
In the event that R-Parity conserving supersymmetry (SUSY) is discovered at
the LHC, a key issue which will need to be addressed will be the consistency of
that signal with astrophysical and non-accelerator constraints on SUSY Dark
Matter. This issue is studied for the SPA benchmark model based on measurements
of end-points and thresholds in the invariant mass spectra of various
combinations of leptons and jets. These measurements are used to constrain the
soft SUSY breaking parameters at the electroweak scale in a general MSSM model.
Based on these constraints, we assess the accuracy with which the Dark Matter
relic density can be measured.Comment: 21 pages, 12 figure
SUSY and Higgs Signatures Implied by Cancellations in
Recent re-evaluations of the Standard Model (SM) contribution to {\mathcal
Br(b\to s\gamma) hint at a positive correction from new physics. Since a
charged Higgs boson exchange always gives a positive contribution to this
branching ratio, the constraint points to the possibility of a relatively light
charged Higgs. It is found that under the HFAG constraints and with
re-evaluated SM results large cancellations between the charged Higgs and the
chargino contributions in supersymmetric models occur. Such cancellations then
correlate the charged Higgs and the chargino masses often implying both are
light. Inclusion of the more recent evaluation of is also
considered. The combined constraints imply the existence of several light
sparticles. Signatures arising from these light sparticles are investigated and
the analysis indicates the possibility of their early discovery at the LHC in a
significant part of the parameter space. We also show that for certain
restricted regions of the parameter space, such as for very large
under the HFAG constraints, the signatures from Higgs production
supersede those from sparticle production and may become the primary signatures
for the discovery of supersymmetry.Comment: Published version. 17 pages, 11 figures. One reference added
RRx-001 followed by platinum plus etoposide in patients with previously treated small-cell lung cancer
BACKGROUND: This exploratory single-arm phase II study evaluated the efficacy and safety of RRx-001 followed by reintroduction of platinum plus etoposide in patients with previously treated small-cell lung cancer (SCLC).
METHODS: Patients were treated with RRx-001 4 mg IV on day 1 of each week of a 21-day cycle followed at progression by re-challenge with etoposide 80-100 IV mg/m
RESULTS: Twenty-six patients were enroled and received at least one dose of RRx-001. The median number of prior lines of therapy was 2 (range 1-9) and 19 (73.1%) patients had platinum-resistant disease. In the intention-to-treat population, one patient (3.8%) had complete response and six (23.1%) had partial response on platinum plus etoposide. The estimated median and 12-month OS from enrolment were 8.6 months and 44.1%, respectively. The most common treatment-emergent adverse event from RRx-001 was mild discomfort at the infusion site (23%).
CONCLUSIONS: RRx-001 followed by re-challenge with platinum plus etoposide chemotherapy is feasible and associated with promising results.
CLINICAL TRIAL REGISTRATION: NCT02489903
Higgs production through gluon fusion: updated cross sections at the Tevatron and the LHC
We present updated predictions for the total cross section for Higgs boson
production by gluon--gluon fusion in hadron collisions. Our calculation
includes the most advanced theoretical information available at present for
this observable: soft-gluon resummation up to next-to-next-to-leading
logarithmic accuracy, the exact treatment of the bottom-quark contribution up
to next-to-leading order, and two-loop electroweak effects. We adopt the most
recent parametrization of parton distribution functions at
next-to-next-to-leading order, and we evaluate the corresponding uncertainties.
In comparison with our previous central predictions, at the Tevatron the
difference ranges from +9% for m_H=115 GeV to -9% for m_H=200 GeV. At the LHC
the cross section is instead significantly increased. The effect goes from +30%
for m_H=115 GeV to +9% for m_H=300 GeV, and is mostly due to the new parton
distribution functions. We also provide new predictions for the LHC at
sqrt{s}=10 TeV.Comment: 7 pages, no figures, references adde
Higgs boson production at the LHC: transverse-momentum resummation and rapidity dependence
We consider Higgs boson production by gluon fusion in hadron collisions. We
study the doubly-differential transverse-momentum (q_T) and rapidity (y)
distribution of the Higgs boson in perturbative QCD. In the region of small q_T
(q_T << M_H, M_H being the mass of the Higgs boson), we include the effect of
logarithmically-enhanced contributions due to multiparton radiation to all
perturbative orders. We use the impact parameter and double Mellin moments to
implement and factorize the multiparton kinematics constraint of transverse-
and longitudinal-momentum conservation. The logarithmic terms are then
systematically resummed in exponential form. At small q_T, we perform the
all-order resummation of large logarithms up to next-to-next-to-leading
logarithmic accuracy, while at large q_T (q_T ~ M_H), we apply a matching
procedure that recovers the fixed-order perturbation theory up to
next-to-leading order. We present quantitative results for the differential
cross section in q_T and y at the LHC, and we comment on the comparison with
the q_T cross section integrated over y.Comment: References adde
A next-to-next-to-leading order calculation of soft-virtual cross sections
We compute the next-to-next-to-leading order (NNLO) soft and virtual QCD
corrections for the partonic cross section of colourless-final state processes
in hadronic collisions. The results are valid to all orders in the dimensional
regularization parameter \ep. The dependence of the results on a particular
process is given through finite contributions to the one and two-loop
amplitudes. To evaluate the accuracy of the soft-virtual approximation we
compare it with the full NNLO result for Drell-Yan and Higgs boson production
via gluon fusion. We also provide a universal expression for the hard
coefficient needed to perform threshold resummation up to
next-to-next-to-leading logarithmic (NNLL) accuracy.Comment: 25 pages, 4 figure
R-parity Conservation via the Stueckelberg Mechanism: LHC and Dark Matter Signals
We investigate the connection between the conservation of R-parity in
supersymmetry and the Stueckelberg mechanism for the mass generation of the B-L
vector gauge boson. It is shown that with universal boundary conditions for
soft terms of sfermions in each family at the high scale and with the
Stueckelberg mechanism for generating mass for the B-L gauge boson present in
the theory, electric charge conservation guarantees the conservation of
R-parity in the minimal B-L extended supersymmetric standard model. We also
discuss non-minimal extensions. This includes extensions where the gauge
symmetries arise with an additional U(1)_{B-L} x U(1)_X, where U(1)_X is a
hidden sector gauge group. In this case the presence of the additional U(1)_X
allows for a Z' gauge boson mass with B-L interactions to lie in the sub-TeV
region overcoming the multi-TeV LEP constraints. The possible tests of the
models at colliders and in dark matter experiments are analyzed including
signals of a low mass Z' resonance and the production of spin zero bosons and
their decays into two photons. In this model two types of dark matter
candidates emerge which are Majorana and Dirac particles. Predictions are made
for a possible simultaneous observation of new physics events in dark matter
experiments and at the LHC.Comment: 38 pages, 7 fig
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