276 research outputs found
QCD Hard Scattering and the Sign of the Spin Asymmetry A_LL^pi
Recent preliminary PHENIX data are consistent with a negative and sizable
longitudinal double-spin asymmetry A_LL^pi for pi^0 production at moderate
transverse momentum p_perp \simeq 1 - 4 GeV and central rapidity. By means of a
systematic investigation of the relevant degrees of freedom we show that the
perturbative QCD framework at leading power in p_perp produces at best a very
small negative asymmetry in this kinematic range.Comment: 4 pages, 3 figures, final version published in PRL (only minor
changes; note: title changed in published version
Higgs boson production in association with top quarks in the POWHEG BOX
We present results from the analytic calculation of top+antitop+Higgs
hadronic production at Next-to-Leading Order in QCD interfaced with
parton-shower Monte Carlo event generators in the POWHEG BOX framework. We
consider kinematic distributions of the top quark and Higgs boson at the 8 TeV
Large Hadron Collider and study the theoretical uncertainties due to specific
choices of renormalization/factorization scales and parton-showering
algorithms, namely PYTHIA and HERWIG. The importance of spin-correlations in
the production and decay stages of a top/antitop quark is discussed on the
example of kinematic distributions of leptons originating from the top/antitop
decays. The corresponding code is now part of the public release of the POWHEG
BOX.Comment: 15 pp, 14 figure
Higgs boson production in association with a photon via weak boson fusion
We present next-to-leading order QCD corrections to Higgs production in
association with a photon via weak boson fusion at a hadron collider. Utilizing
the fully flexible parton level Monte-Carlo program VBFNLO, we find small
overall corrections, while the shape of some distributions is sensitive to
radiative contributions in certain regions of phase-space. Residual scale
uncertainties at next-to-leading order are at the few-percent level. Being
perturbatively well under control and exhibiting kinematic features that allow
to distinguish it from potential backgrounds, this process can serve as a
valuable source of information on the Yukawa coupling.Comment: 8 pages. To appear in the proceedings of the "Photon 2011" conference
held in Spa, Belgium Added reference to arXiv:1105.0920 [hep-ph
Electricity markets: Designing auctions where suppliers have uncertain costs
We analyse how the market design influences the bidding behaviour in multi-unit auctions, such as wholesale electricity markets. It is shown that competition improves for increased market transparency and we identify circumstances where the auctioneer prefers uniform to discriminatory pricing. We note that political risks could significantly worsen competition in hydro-dominated markets. It would be beneficial for such markets to have clearly defined contingency plans for extreme market situations.market transparenc
A Community of Practice: Librarians in a Biomedical Research Network
Providing library and reference services within a biomedical research community presents special challenges for librarians, especially those in historically lower-funded states. These challenges can include understanding needs, defining and communicating the library’s role, building relationships, and developing and maintaining general and subject specific knowledge. This article describes a biomedical research network and the work of health sciences librarians at the lead intensive research institution with librarians from primarily undergraduate institutions and tribal colleges and universities. Applying the concept of a “community of practice” to a collaborative effort suggests how librarians can work together to provide effective reference services to researchers in biomedicine
Hadronic production of top-quark pairs in association with a pair of leptons in the POWHEG BOX framework
We present an implementation of ()
hadronic production at next-to-leading order in QCD matched to parton-shower
event generators in the POWHEG BOX framework. The program we developed includes
all leading-order contributions of order for the specified
final state, as well as the corresponding first-order QCD corrections. Decays
of the top quarks have been simulated retaining spin-correlations in all
tree-level matrix elements. We consider the case of the Large Hadron Collider
at TeV and compare results for production
in the fiducial volume where the invariant mass of the lepton pairs is centered
around the -boson mass to corresponding predictions for on-shell
production with . We find that off-shell effects in
are in general small at the level of the total cross
section, but can decrease the tail of the leptons' transverse momentum
distributions by 10-20% and, in these regions, they are visible beyond the
scale uncertainty due to renormalization and factorization scale variation.
Moreover, we find that accounting for top-quark decays in the narrow-width
approximation with tree-level spin correlations also gives origin to 10-20%
effects in specific regions of the kinematic distributions of the decayed final state.Comment: 22 pages, 13 figure
Next-to-leading order QCD corrections to Higgs boson production in association with a photon via weak-boson fusion at the LHC
Higgs boson production in association with a hard central photon and two
forward tagging jets is expected to provide valuable information on Higgs boson
couplings in a range where it is difficult to disentangle weak-boson fusion
processes from large QCD backgrounds. We present next-to-leading order QCD
corrections to Higgs production in association with a photon via weak-boson
fusion at a hadron collider in the form of a flexible parton-level Monte Carlo
program. The QCD corrections to integrated cross sections are found to be small
for experimentally relevant selection cuts, while the shape of kinematic
distributions can be distorted by up to 20% in some regions of phase space.
Residual scale uncertainties at next-to-leading order are at the few-percent
level.Comment: 17 pages, 7 figures, 1 tabl
Next-to-leading order QCD corrections to electroweak Zjj production in the POWHEGBOX
We present an implementation of electroweak Z-boson production in association
with two jets at hadron colliders in the POWHEG framework, a method that allows
the interfacing of NLO-QCD calculations with parton-shower Monte Carlo
programs. We focus on the leptonic decays of the weak gauge boson, and take
photonic and non-resonant contributions to the matrix elements fully into
account. We provide results for observables of particular importance for the
suppression of QCD backgrounds to vector-boson fusion processes by means of
central-jet-veto techniques. While parton-shower effects are small for most
observables associated with the two hardest jets, they can be more pronounced
for distributions that are employed in central-jet-veto studies.Comment: 12 pages, 5 figure
Методика використання фізичних задач в курсі охорона праці
(uk) У статті розкривається важливість розв’язання фізичних задач в курсі охорона праці. Використання фізичних задач забезпечить повноцінне засвоєння навчального матеріалу з курсу.(en) In the article importance of of physicaltasks opens up in a course labour protection. The use of physical tasks will provide the valuable mastering of educational material from a course
Cervical and ocular vestibular evoked myogenic potential : a comparison of narrowband chirp, broadband chirp, tone burst and click stimulation
OBJECTIVES :
To compare the response rate and response parameters of cervical and ocular vestibular evoked myogenic potentials (c&oVEMP) elicited by narrowband (NB) and broadband (BB) CE-Chirp, with the more classical tone burst (TB) and click VEMPs.
DESIGN :
The response rate, latency, amplitude and asymmetry ratio of c&oVEMPs elicited by 95 dB nHL air conducted (AC) 500 Hz NB CE-chirp, BB CE-chirp, 500 Hz TB and click stimuli were recorded bilaterally.
STUDY SAMPLE :
20 male and 38 female participants (19–39 years).
RESULTS :
For the cVEMP, the highest response rate was found for NB chirp (100%), followed by TB (91%), BB chirp (87%) and finally click (85%). A similar order was seen for oVEMP with percentages of 100%; 57%, 57%, and 43%. The 500 Hz NB CE-Chirp elicited significantly shorter cVEMP P1 and N1 latencies and significantly larger c&oVEMP amplitudes compared to all other stimuli. BB CE-Chirp elicited significantly shorter c&oVEMP P1 and N1 latencies with smaller amplitudes compared to TB. Asymmetry ratios were not statistically significant for all comparisons.
CONCLUSION :
The 500 Hz NB CE-chirp provides the highest response rates, shorter latencies and larger amplitudes, and therefore seem a promising stimulus for reliably measuring c&oVEMPs in clinical practice.http://www.tandfonline.com/loi/iija20hj2024Speech-Language Pathology and AudiologySDG-03:Good heatlh and well-bein
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