69 research outputs found
Model-independent measurement of the top quark polarisation
We introduce a new asymmetry in the decay t -> W b -> l nu b, which is shown
to be directly proportional to the polarisation of the top quark along a chosen
axis, times a sum of W helicity fractions. The latter have already been
precisely measured at the Tevatron and the Large Hadron Collider. Therefore,
this new asymmetry can be used to obtain a model-independent measurement of the
polarisation of top quarks produced in any process at hadron or lepton
colliders.Comment: LaTeX 12 pages. Discussion expanded with a new plot, references
added. Final version to appear in PL
An observation of a new class of afterpulses with delay time in the range of 70-200 microseconds in classical vacuum photomultipliers
We present results of the first observation of afterpulses with extremely
long (~120 microseconds) delay time from the main pulse in 8 inch classical
vacuum photomultipliers.Comment: To be published in NIM
The SUSY-QCD beta function to three loops
A number of DR-bar renormalization constants in softly broken SUSY-QCD are
evaluated to three-loop level: the wave function renormalization constants for
quarks, squarks, gluons, gluinos, ghosts, and epsilon-scalars, and the
renormalization constants for the quark and gluino mass as well as for all
cubic vertices. The latter allow us to derive the corresponding beta functions
through three loops, all of which we find to be identical to the expression for
the gauge beta function obtained by Jack, Jones, and North [Jack:1996vg] (see
also Ref. [Pickering:2001aq]). This explicitely demonstrates the consistency of
DRED with SUSY and gauge invariance, an important pre-requisite for precision
calculations in supersymmetric theories.Comment: Latex, 16 pages, reference added; v2: matches published version in
Eur.Phys.J.
Far-infrared optical excitations in multiferroic TbMnO_3
We provide a detailed study of the reflectivity of multiferroic TbMnO_3 for
wave numbers from 40 cm^{-1} to 1000 cm^{-1} and temperatures 5 K < T < 300 K.
Excitations are studied for polarization directions E || a, the polarization
where electromagnons are observed, and for E || c, the direction of the
spontaneous polarization in this material. The temperature dependencies of
eigenfrequencies, damping constants and polar strengths of all modes are
studied and analyzed. For E || a and below the spiral ordering temperature of
about 27 K we observe a transfer of optical weight from phonon excitations to
electromagnons, which mainly involves low-frequency phonons. For E || c an
unusual increase of the total polar strength and hence of the dielectric
constant is observed indicating significant transfer of dynamic charge probably
within manganese-oxygen bonds on decreasing temperatures.Comment: 8 pages, 7 figures, accepted for submission in European Physical
Journal
Double-exchange model study of multiferroic MnO perovskites
In this proceeding, recent theoretical investigations by the authors on the
multiferroic MnO perovskites are briefly reviewed at first. Using the
double-exchange model, the realistic spiral spin order in undoped manganites
such as TbMnO and DyMnO is well reproduced by incorporating a weak
next-nearest neighbor superexchange ( of nearest neighbor
superexchange) and moderate Jahn-Teller distortion. The phase transitions from
the A-type antiferromagnet (as in LaMnO), to the spiral phase (as in
TbMnO), and finally to the E-type antiferromagnet (as in HoMnO), with
decreasing size of the ions, were also explained. Moreover, new results of
phase diagram of the three-dimensional lattice are also included. The
ferromagnetic tendency recently discovered in the LaMnO and TbMnO thin
films is explained by considering the substrate stress. Finally, the
relationship between our double-exchange model and a previously used
-- model is further discussed from the perspective of spin wave
excitations.Comment: 6 pages, 3 figures; Proceeding of the Workshop on Magnetoelectric
Interaction Phenomena in Crystals (MEIPIC-6); To be appeared in European
Physical Journal
Standard Model backgrounds to supersymmetry searches
This work presents a review of the Standard Model sources of backgrounds to
the search of supersymmetry signals. Depending on the specific model, typical
signals may include jets, leptons, and missing transverse energy due to the
escaping lightest supersymmetric particle. We focus on the simplest case of
multijets and missing energy, since this allows us to expose most of the issues
common to other more complex cases. The review is not exhaustive, and is aimed
at collecting a series of general comments and observations, to serve as
guideline for the process that will lead to a complete experimental
determination of size and features of such SM processes.Comment: To appear in the J. Wess memorial volume, "Supersymmetry on the Eve
of the LHC", to be published in European Physical Journal
Team dynamics in emergency surgery teams: results from a first international survey
Background: Emergency surgery represents a unique context. Trauma teams are often multidisciplinary and need to operate under extreme stress and time constraints, sometimes with no awareness of the trauma\u2019s causes or the patient\u2019s personal and clinical information. In this perspective, the dynamics of how trauma teams function is fundamental to ensuring the best performance and outcomes. Methods: An online survey was conducted among the World Society of Emergency Surgery members in early 2021. 402 fully filled questionnaires on the topics of knowledge translation dynamics and tools, non-technical skills, and difficulties in teamwork were collected. Data were analyzed using the software R, and reported following the Checklist for Reporting Results of Internet E-Surveys (CHERRIES). Results: Findings highlight how several surgeons are still unsure about the meaning and potential of knowledge translation and its mechanisms. Tools like training, clinical guidelines, and non-technical skills are recognized and used in clinical practice. Others, like patients\u2019 and stakeholders\u2019 engagement, are hardly implemented, despite their increasing importance in the modern healthcare scenario. Several difficulties in working as a team are described, including the lack of time, communication, training, trust, and ego. Discussion: Scientific societies should take the lead in offering training and support about the abovementioned topics. Dedicated educational initiatives, practical cases and experiences, workshops and symposia may allow mitigating the difficulties highlighted by the survey\u2019s participants, boosting the performance of emergency teams. Additional investigation of the survey results and its characteristics may lead to more further specific suggestions and potential solutions
Measurements of the t(t)Overbar charge asymmetry using the dilepton decay channel in pp collisions at root s=7 TeV
The ttÂŻ charge asymmetry in proton-proton collisions at s√ = 7 TeV is measured using the dilepton decay channel (ee, e μ , or μμ ). The data correspond to a total integrated luminosity of 5.0 fb −1 , collected by the CMS experiment at the LHC. The tt and lepton charge asymmetries, defined as the differences in absolute values of the rapidities between the reconstructed top quarks and antiquarks and of the pseudorapidities between the positive and negative leptons, respectively, are measured to be A C = −0 . 010 ± 0 . 017 (stat . ) ± 0 . 008 (syst . ) and AlepC = 0 . 009 ± 0 . 010 (stat . ) ± 0 . 006 (syst . ). The lepton charge asymmetry is also measured as a function of the invariant mass, rapidity, and transverse momentum of the ttÂŻ system. All measurements are consistent with the expectations of the standard model
Search for the Standard Model Higgs boson decaying into bbÂŻ produced in association with top quarks decaying hadronically in pp collisions at âs = 8 TeV with the ATLAS detector
A search for Higgs boson production in association with a pair of top quarks (ttÂŻ H) is performed, where the Higgs boson decays to bbÂŻ, and both top quarks decay hadronically. The data used correspond to an integrated luminosity of 20.3 fbâ1 of pp collisions at âs = 8 TeV collected with the ATLAS detector at the Large Hadron Collider. The search selects events with at least six energetic jets and uses a boosted decision tree algorithm to discriminate between signal and Standard Model background. The dominant multijet background is estimated using a dedicated data-driven technique. For a Higgs boson mass of 125 GeV, an upper limit of 6.4 (5.4) times the Standard Model cross section is observed (expected) at 95% confidence level. The best-fit value for the signal strength is ÎŒ = 1.6 ± 2.6 times the Standard Model expectation for mH = 125 GeV. Combining all ttÂŻ H searches carried out by ATLAS at âs = 8 and 7 TeV, an observed (expected) upper limit of 3.1 (1.4) times the Standard Model expectation is obtained at 95% confidence level, with a signal strength ÎŒ = 1.7 ± 0.8
International nosocomial infection control consortium (INICC) report, data summary of 36 countries, for 2004-2009
The results of a surveillance study conducted by the International Nosocomial Infection Control Consortium (INICC) from January 2004 through December 2009 in 422 intensive care units (ICUs) of 36 countries in Latin America, Asia, Africa, and Europe are reported. During the 6-year study period, using Centers for Disease Control and Prevention (CDC) National Healthcare Safety Network (NHSN; formerly the National Nosocomial Infection Surveillance system [NNIS]) definitions for device-associated health care-associated infections, we gathered prospective data from 313,008 patients hospitalized in the consortium's ICUs for an aggregate of 2,194,897 ICU bed-days. Despite the fact that the use of devices in the developing countries' ICUs was remarkably similar to that reported in US ICUs in the CDC's NHSN, rates of device-associated nosocomial infection were significantly higher in the ICUs of the INICC hospitals; the pooled rate of central line-associated bloodstream infection in the INICC ICUs of 6.8 per 1,000 central line-days was more than 3-fold higher than the 2.0 per 1,000 central line-days reported in comparable US ICUs. The overall rate of ventilator-associated pneumonia also was far higher (15.8 vs 3.3 per 1,000 ventilator-days), as was the rate of catheter-associated urinary tract infection (6.3 vs. 3.3 per 1,000 catheter-days). Notably, the frequencies of resistance of Pseudomonas aeruginosa isolates to imipenem (47.2% vs 23.0%), Klebsiella pneumoniae isolates to ceftazidime (76.3% vs 27.1%), Escherichia coli isolates to ceftazidime (66.7% vs 8.1%), Staphylococcus aureus isolates to methicillin (84.4% vs 56.8%), were also higher in the consortium's ICUs, and the crude unadjusted excess mortalities of device-related infections ranged from 7.3% (for catheter-associated urinary tract infection) to 15.2% (for ventilator-associated pneumonia). Copyright © 2012 by the Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved
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