275 research outputs found
A randomized, phase II trial of two dose schedules of carboplatin/paclitaxel/cetuximab in stage IIIB/IV non-small-cell lung cancer (NSCLC)
Background: This trial investigated the efficacy and safety of weekly cetuximab combined with two different schedules of paclitaxel/carboplatin for stage IIIB/IV non-small-cell lung cancer (NSCLC). Methods: A total of 168 patients with previously untreated stage IIIB/IV NSCLC were randomized to arm A, cetuximab (400 mg/m2 day 1 followed by weekly 250 mg/m2) + paclitaxel (Taxol) (225 mg/m2)/carboplatin (AUC6) day 1 every 3 weeks or arm B, same cetuximab regimen plus paclitaxel (100 mg/m2) days 1, 8, and 15 every 3 weeks and carboplatin (AUC6) day 1 every 4 weeks. Treatment continued for a four-cycle maximum. Patients with a complete response, partial response, or stable disease after four cycles could receive cetuximab 250 mg/m2/week until disease progression or unacceptable toxicity. The primary end point was to evaluate progression-free survival (PFS). Results: Median PFS was 4.7 and 4.3 months for arms A and B, respectively (6-month PFS, 27.3% versus 30.9%). Median overall survival was 11.4 versus 9.8 months for arms A and B, respectively; estimated 1-year survival, 47.7% versus 39.3%; and objective response rate, 29.6% versus 25%. The regimen was well tolerated with rash and hematologic toxicity being most common. Conclusions: This study did not meet the prespecified benchmark of 35% 6-month PFS rate; both combination schedules of cetuximab plus paclitaxel/carboplatin were feasible and equivalent for treating advanced NSCLC
A Positive-Weight Next-to-Leading-Order Monte Carlo for Z Pair Hadroproduction
We present a first application of a previously published method for the
computation of QCD processes that is accurate at next-to-leading order, and
that can be interfaced consistently to standard shower Monte Carlo programs. We
have considered Z pair production in hadron-hadron collisions, a process whose
complexity is sufficient to test the general applicability of the method. We
have interfaced our result to the HERWIG and PYTHIA shower Monte Carlo
programs. Previous work on next-to-leading order corrections in a shower Monte
Carlo (the MC@NLO program) may involve the generation of events with negative
weights, that are avoided with the present method. We have compared our results
with those obtained with MC@NLO, and found remarkable consistency. Our method
can also be used as a standalone, alternative implementation of QCD
corrections, with the advantage of positivity, improved convergence, and
next-to-leading logarithmic accuracy in the region of small transverse momentum
of the radiated parton.Comment: 33 pages, 10 figure
Transient elastohydrodynamic lubrication analysis of a novel metal-on-metal hip prosthesis with a non-spherical femoral bearing surface
Effective lubrication performance of metal-on-metal hip implants only requires optimum conformity within the main loaded area, while it is advantageous to increase the clearance in the equatorial region. Such a varying clearance can be achieved by using non-spherical bearing surfaces for either acetabular or femoral components. An elastohydrodynamic lubrication model of a novel metal-on-metal hip prosthesis using a non-spherical femoral bearing surface against a spherical cup was solved under loading and motion conditions specified by ISO standard. A full numerical methodology of considering the geometric variation in the rotating non-spherical head in elastohydrodynamic lubrication solution was presented, which is applicable to all non-spherical head designs. The lubrication performance of a hip prosthesis using a specific non-spherical femoral head, Alpharabola, was analysed and compared with those of spherical bearing surfaces and a non-spherical Alpharabola cup investigated in previous studies. The sensitivity of the lubrication performance to the anteversion angle of the Alpharabola head was also investigated. Results showed that the non-spherical head introduced a large squeeze-film action and also led to a large variation in clearance within the loaded area. With the same equatorial clearance, the lubrication performance of the metal-on-metal hip prosthesis using an Alpharabola head was better than that of the conventional spherical bearings but worse than that of the metal-on-metal hip prosthesis using an Alpharabola cup. The reduction in the lubrication performance caused by the initial anteversion angle of the non-spherical head was small, compared with the improvement resulted from the non-spherical geometry
Matching matrix elements and shower evolution for top-quark production in hadronic collisions
We study the matching of multijet matrix elements and shower evolution in the
case of top production in hadronic collisions at the Tevatron and at the LHC.
We present the results of the matching algorithm implemented in the ALPGEN
Monte Carlo generator, and compare them with results obtained at the parton
level, and with the predictions of the MC@NLO approach. We highlight the
consistency of the matching algorithm when applied to these final states, and
the excellent agreement obtained with MC@NLO for most inclusive quantities. We
nevertheless identify also a remarkable difference in the rapidity spectrum of
the leading jet accompanying the top quark pair, and comment on the likely
origin of this discrepancy.Comment: 22 pages, 13 figures, 5 tables. JHEP styl
The BCS-Bose Crossover Theory
We contrast {\it four} distinct versions of the BCS-Bose statistical
crossover theory according to the form assumed for the electron-number equation
that accompanies the BCS gap equation. The four versions correspond to
explicitly accounting for two-hole-(2h) as well as two-electron-(2e) Cooper
pairs (CPs), or both in equal proportions, or only either kind. This follows
from a recent generalization of the Bose-Einstein condensation (GBEC)
statistical theory that includes not boson-boson interactions but rather 2e-
and also (without loss of generality) 2h-CPs interacting with unpaired
electrons and holes in a single-band model that is easily converted into a
two-band model. The GBEC theory is essentially an extension of the
Friedberg-T.D. Lee 1989 BEC theory of superconductors that excludes 2h-CPs. It
can thus recover, when the numbers of 2h- and 2e-CPs in both BE-condensed and
noncondensed states are separately equal, the BCS gap equation for all
temperatures and couplings as well as the zero-temperature BCS
(rigorous-upper-bound) condensation energy for all couplings. But ignoring
either 2h- {\it or} 2e-CPs it can do neither. In particular, only {\it half}
the BCS condensation energy is obtained in the two crossover versions ignoring
either kind of CPs. We show how critical temperatures from the original
BCS-Bose crossover theory in 2D require unphysically large couplings for the
Cooper/BCS model interaction to differ significantly from the s of
ordinary BCS theory (where the number equation is substituted by the assumption
that the chemical potential equals the Fermi energy).Comment: thirteen pages including two figures. Physica C (in press, 2007
Magnetic Field Amplification in Galaxy Clusters and its Simulation
We review the present theoretical and numerical understanding of magnetic
field amplification in cosmic large-scale structure, on length scales of galaxy
clusters and beyond. Structure formation drives compression and turbulence,
which amplify tiny magnetic seed fields to the microGauss values that are
observed in the intracluster medium. This process is intimately connected to
the properties of turbulence and the microphysics of the intra-cluster medium.
Additional roles are played by merger induced shocks that sweep through the
intra-cluster medium and motions induced by sloshing cool cores. The accurate
simulation of magnetic field amplification in clusters still poses a serious
challenge for simulations of cosmological structure formation. We review the
current literature on cosmological simulations that include magnetic fields and
outline theoretical as well as numerical challenges.Comment: 60 pages, 19 Figure
Characterisation of the muon beams for the Muon Ionisation Cooling Experiment
A novel single-particle technique to measure emittance has been developed and used to characterise seventeen different muon beams for the Muon Ionisation Cooling Experiment (MICE). The muon beams, whose mean momenta vary from 171 to 281 MeV/c, have emittances of approximately 1.2–2.3 π mm-rad horizontally and 0.6–1.0 π mm-rad vertically, a horizontal dispersion of 90–190 mm and momentum spreads of about 25 MeV/c. There is reasonable agreement between the measured parameters of the beams and the results of simulations. The beams are found to meet the requirements of MICE
PYTHIA 6.4 Physics and Manual
The PYTHIA program can be used to generate high-energy-physics `events', i.e.
sets of outgoing particles produced in the interactions between two incoming
particles. The objective is to provide as accurate as possible a representation
of event properties in a wide range of reactions, within and beyond the
Standard Model, with emphasis on those where strong interactions play a role,
directly or indirectly, and therefore multihadronic final states are produced.
The physics is then not understood well enough to give an exact description;
instead the program has to be based on a combination of analytical results and
various QCD-based models. This physics input is summarized here, for areas such
as hard subprocesses, initial- and final-state parton showers, underlying
events and beam remnants, fragmentation and decays, and much more. Furthermore,
extensive information is provided on all program elements: subroutines and
functions, switches and parameters, and particle and process data. This should
allow the user to tailor the generation task to the topics of interest.Comment: 576 pages, no figures, uses JHEP3.cls. The code and further
information may be found on the PYTHIA web page:
http://www.thep.lu.se/~torbjorn/Pythia.html Changes in version 2: Mistakenly
deleted section heading for "Physics Processes" reinserted, affecting section
numbering. Minor updates to take into account referee comments and new colour
reconnection option
Heavy quarkonium: progress, puzzles, and opportunities
A golden age for heavy quarkonium physics dawned a decade ago, initiated by
the confluence of exciting advances in quantum chromodynamics (QCD) and an
explosion of related experimental activity. The early years of this period were
chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in
2004, which presented a comprehensive review of the status of the field at that
time and provided specific recommendations for further progress. However, the
broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles
could only be partially anticipated. Since the release of the YR, the BESII
program concluded only to give birth to BESIII; the -factories and CLEO-c
flourished; quarkonium production and polarization measurements at HERA and the
Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the
deconfinement regime. All these experiments leave legacies of quality,
precision, and unsolved mysteries for quarkonium physics, and therefore beg for
continuing investigations. The plethora of newly-found quarkonium-like states
unleashed a flood of theoretical investigations into new forms of matter such
as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the
spectroscopy, decays, production, and in-medium behavior of c\bar{c}, b\bar{b},
and b\bar{c} bound states have been shown to validate some theoretical
approaches to QCD and highlight lack of quantitative success for others. The
intriguing details of quarkonium suppression in heavy-ion collisions that have
emerged from RHIC have elevated the importance of separating hot- and
cold-nuclear-matter effects in quark-gluon plasma studies. This review
systematically addresses all these matters and concludes by prioritizing
directions for ongoing and future efforts.Comment: 182 pages, 112 figures. Editors: N. Brambilla, S. Eidelman, B. K.
Heltsley, R. Vogt. Section Coordinators: G. T. Bodwin, E. Eichten, A. D.
Frawley, A. B. Meyer, R. E. Mitchell, V. Papadimitriou, P. Petreczky, A. A.
Petrov, P. Robbe, A. Vair
Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS
We present the results of a search for new, heavy particles that decay at a
significant distance from their production point into a final state containing
charged hadrons in association with a high-momentum muon. The search is
conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV
and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS
detector operating at the Large Hadron Collider. Production of such particles
is expected in various scenarios of physics beyond the standard model. We
observe no signal and place limits on the production cross-section of
supersymmetric particles in an R-parity-violating scenario as a function of the
neutralino lifetime. Limits are presented for different squark and neutralino
masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final
version to appear in Physics Letters
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