3,827 research outputs found
Temperature and Magnetic Field Dependencies of Condon Domain Phase in Lifschitz-Kosevich-Shoenberg Approximation
The temperature and magnetic field behavior of non-uniform diamagnetic phase
of strongly correlated electron gas at the conditions of dHvA effect is
analyzed. It is shown, that in the framework of Lifschitz-Kosevich-Shoenberg
approximation the magnetic induction splitting, as well as the range of
existence of Condon domains, are characterized by strong dependencies on
temperature, magnetic field and impurities of the sample.Comment: 7 pages, 7 figure
Diamagnetic Phase Transition and Phase Diagrams in Beryllium
The model of diamagnetic phase transition in beryllium which takes into
account the quasi 2-dimensional shape of the Fermi surface of beryllium is
proposed. It explains correctly the recent experimental data on observation of
non-homogeneous phase in beryllium at the conditions of strong dHvA effect when
the strong correlation of electron gas results in instability of homogeneous
phase and formation of Condon domain structure.Comment: 5 pages, 4 figure
Inclusive One- and Two-Jet Cross sections in Reactions at Colliders
We have calculated inclusive one-- and two--jet production in photon--photon
collisions superimposing direct, single resolved and double resolved cross
sections for center of mass energies of the LEP1, LEP2 and NLC range. The
direct and single resolved cross sections are calculated up to
next--to--leading order. The double resolved two--jet cross section is
calculated only in LO with a factor estimated from the NLO one--jet cross
section. Various differential cross sections as functions of transverse momenta
and rapidities of the jets are evaluated.Comment: 25 pages, latex, 15 figures appended as uuencoded fil
Family-witnessed resuscitation in emergency departments: Doctorsâ attitudes and practices
Background. Resuscitation of patients occurs daily in emergency departments. Traditional practice entails family members remaining outside the resuscitation room. Objective. We explored the introduction of family-witnessed resuscitation (FWR) as it has been shown to allow closure for the family when resuscitation is unsuccessful and helps them to better understand the last moments of life. Results. Attending medical doctors have concerns about this practice, such as traumatisation of family members, increased pressure on the medical team, interference by the family, and potential medico-legal consequences. There was not complete acceptance of the practice of FWR among the sample group. Conclusion. Short-course training such as postgraduate advanced life support and other continued professional development activities should have a positive effect on this practice. The more experienced doctors are and the longer they work in emergency medicine, the more comfortable they appear to be with the concept of FWR and therefore the more likely they are to allow it. Further study and course attendance by doctors has a positive influence on the practice of FWR
Collinear Subtractions in Hadroproduction of Heavy Quarks
We present a detailed discussion of the collinear subtraction terms needed to
establish a massive variable-flavour-number scheme for the one-particle
inclusive production of heavy quarks in hadronic collisions. The subtraction
terms are computed by convoluting appropriate partonic cross sections with
perturbative parton distribution and fragmentation functions relying on the
method of mass factorization. We find (with one minor exception) complete
agreement with the subtraction terms obtained in a previous publication by
comparing the zero-mass limit of a fixed-order calculation with the genuine
massles results in the MSbar scheme. This presentation will be useful for
extending the massive variable-flavour-number scheme to other processes.Comment: 29 pages, 17 figures include
Spin Dependent Drell-Yan beyond Leading Order: Non-Singlet Virtual corrections to
We present parton-level analytical results for the next-to-leading order
non-singlet virtual and real corrections to the Drell-Yan differential
cross-section. The dependence of the differential cross section on the helicity
of the initial state partons is shown explicitly (the spins of the final state
partons are summed). The calculation is implemented in dimensional
regularization within the scheme and with the t'Hooft Veltman
prescriptions for the n-dimensional . Both the polarized initial
state and the unpolarized cross sections can be obtained from our result. Our
unpolarized cross section agrees with the previous result of Ellis, Martinelli
and Petronzio in the non-singlet sector.Comment: 12 pages, 7 figures, one chapter added, change in figure
Spin Dependent Drell Yan in QCD to (I). (The Non-Singlet Sector)
A study of the order corrections to the Drell Yan (non-singlet)
cross section for incoming states of arbitrary longitudinal helicities is
presented. The study is performed in the case of the transverse momentum
distributions, , of the lepton pair and extends the calculation of Ellis
Martinelli and Petronzio (EMP) to the polarized case. We use the
scheme and the t'Hooft-Veltman regularization for the helicity projectors. From
our results one can obtain the bulk of the totally inclusive NNLO cross section
for the production of a Drell Yan pair in the non-singlet sector by a simple
integration over the heavy photon momentum. We show that in the
helicity is not conserved, unless a finite renormalization is done to reenter
into a physical scheme (). This aspect of the calculation follows
the same trend as in polarized production of single and double photon to
. In the unpolarized limit we reproduce all the results of EMP.Comment: 39 pages, 7 figures (included
Probing the parton densities of virtual photons with the reaction gamma^*gamma->jets at LEP
We present a next-to-leading order calculation of jet production in
gamma^*gamma collisions from e+e- scattering in a region where the virtuality
Q^2 of the probing virtual photon is small compared to the transverse jet
energy. The calculation is based on the phase-space slicing method. The initial
state singularity of the virtual photon is factorized into the structure
function of the virtual photon, using the MS-bar factorization scheme for
virtual photons. Numerical results are presented for LEP2 conditions. The
perturbative stability of the pure direct virtual photon approach is compared
to that of including resolved virtual photons in different regions of Q^2. We
make predictions for cross sections which suggest that different
parametrizations of virtual photon parton densities should be distinguishable
by measurements of jet cross sections at LEP.Comment: 19 pages, 8 eps figue
Large- Heavy-Quark Production in Two-Photon Collisions
The next-to-leading-order (NLO) cross section for the production of heavy
quarks at large transverse momenta () in collisions is
calculated with perturbative fragmentation functions (PFF's). This approach
allows for a resummation of terms which
arise in NLO from collinear emission of gluons by heavy quarks at large
or from almost collinear branching of photons or gluons into
heavy-quark pairs. We present single-inclusive distributions in and
rapidity including direct and resolved photons for production of
heavy quarks at colliders and at high-energy colliders.
The results are compared with the fixed-order calculation for finite
including QCD radiative corrections. The two approaches differ in the
definitions and relative contributions of the direct and resolved terms, but
essentially agree in their sum. The resummation of the terms in the PFF approach leads to a softer
distribution and to a reduced sensitivity to the choice of the renormalization
and factorization scales.Comment: 17 pages, Latex, epsf, 7 figures appended as uuencoded file (hardcopy
can be obtained upon request from [email protected]
Jet photoproduction at HERA
We compute various kinematical distributions for one-jet and two-jet
inclusive photoproduction at HERA. Our results are accurate to next-to-leading
order in QCD. We use the subtraction method for the cancellation of infrared
singularities. We perform a thorough study of the reliability of QCD
predictions; in particular, we consider the scale dependence of our results and
discuss the cases when the perturbative expansion might break down. We also
deal with the problem of the experimental definition of the pointlike and
hadronic components of the incident photon, and briefly discuss the sensitivity
of QCD predictions upon the input parameters of the calculation, like
and the parton densities.Comment: 26 pages Latex, uses epsfig.sty, 24 eps figures include
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