241 research outputs found
Study of certain features of the electronic structure of the ternary alloys Ni2(Mn, Fe) and Ni3(Mn, Co)
The changes in electronic structure related to transport processes occurring during the alloying of he alloy Ni3Mn with iron and cobalt, and the ordering of the ternary alloys thus formed are presented. The Hall effect, the absolute thermal emf, the internal saturation induction, the Nernst-Ettingshausen constant, and the electrical resistivity were measured. Results show a decrease in the contribution of hole sections of the Fermi surface to the transport process occurs together with a considerable increase in the contribution of electron sections. In this case, the mobility of 3 dimensional holes decreases and the mobility of 4s electrons increases considerably
Rapidity-Separation Dependence and the Large Next-to-Leading Corrections to the BFKL Equation
Recent concerns about the very large next-to-leading logarithmic (NLL)
corrections to the BFKL equation are addressed by the introduction of a
physical rapidity-separation parameter . At the leading logarithm (LL)
this parameter enforces the constraint that successive emitted gluons have a
minimum separation in rapidity, . The most significant
effect is to reduce the BFKL Pomeron intercept from the standard result as
is increased from 0 (standard BFKL). At NLL this -dependence
is compensated by a modification of the BFKL kernel, such that the total
dependence on is formally next-to-next-to-leading logarithmic. In this
formulation, as long as (for ): (i) the NLL
BFKL pomeron intercept is stable with respect to variations of , and
(ii) the NLL correction is small compared to the LL result. Implications for
the applicability of the BFKL resummation to phenomenology are considered.Comment: 16 pages, 3 figures, Late
Infrared safety of impact factors for colourless particle interactions
We demonstrate, to next-to-leading order accuracy, the cancellation of the
infrared singularities in the impact factors which arise in the QCD description
of high energy processes A + B -> A' + B' of colourless particles. We study the
example where A is a virtual photon in detail, but show that the result is true
in general.Comment: 31 pages latex including 10 figure
NLO Corrections to the kernel of the BKP-equations
We present results for the NLO kernel of the BKP equations for composite
states of three reggeized gluons in the Odderon channel, both in QCD and in N=4
SYM. The NLO kernel consists of the NLO BFKL kernel in the color octet
representation and the connected kernel, computed in the tree
approximation.Comment: 28 pages, 7 figure
Virtual Next-to-Leading Corrections to the Lipatov Vertex
We compute the virtual next-to-leading corrections to the Lipatov vertex in
the helicity-amplitude formalism. These agree with previous results by Fadin
and collaborators, in the conventional dimensional-regularization scheme. We
discuss the choice of reggeization scale in order to minimize its impact on the
next-to-leading-logarithmic corrections to the BFKL equation.Comment: Latex, 20 pages, no figures; One minor typo fixed. References added.
To be published in Phys. Rev.
Symmetry Properties of the Effective Action for High-Energy Scattering in QCD
We study the effective action describing high-energy scattering processes in
the multi-Regge limit of QCD, which should provide the starting point for a new
attempt to overcome the limitations of the leading logarithmic and the eikonal
approximations. The action can be obtained via simple graphical rules or by
integrating in the QCD functional integral over momentum modes of gluon and
quark fields that do not appear explicitely as scattering or exchanged
particles in the considered processes. The supersymmetry is used to obtain the
terms in the action involving quarks fields from the pure gluonic ones. We
observe a Weizs\"acker - Williams type relations between terms describing
scattering and production of particles.Comment: 37 pages LATEX, 1 Table and 7 figures using package FEYNMA
The spread of the gluon k_t-distribution and the determination of the saturation scale at hadron colliders in resummed NLL BFKL
The transverse momentum distribution of soft hadrons and jets that accompany
central hard-scattering production at hadron colliders is of great importance,
since it has a direct bearing on the ability to separate new physics signals
from Standard Model backgrounds. We compare the predictions for the gluonic
k_t-distribution using two different approaches: resummed NLL BFKL and DGLAP
evolution. We find that as long as the initial and final virtualities (k_t)
along the emission chain are not too close to each other, the NLL resummed BFKL
results do not differ significantly from those obtained using standard DGLAP
evolution. The saturation momentum Q_s(x), calculated within the resummed BFKL
approach, grows with 1/x even slower than in the leading-order DGLAP case.Comment: 24 pages, 8 figures, An improved, slightly more precise NLL
resummation is used and the figures are updated accordingly. The conclusions
are unchange
High-Energy QCD Asymptotics of Photon-Photon Collisions
The high-energy behaviour of the total cross section for highly virtual
photons, as predicted by the BFKL equation at next-to-leading order (NLO) in
QCD, is discussed. The NLO BFKL predictions, improved by the BLM optimal scale
setting, are in good agreement with recent OPAL and L3 data at CERN LEP2. NLO
BFKL predictions for future linear colliders are presented.Comment: Latex, 7 pages, 4 figure
Single jet and prompt-photon inclusive production with multi-Regge kinematics: From Tevatron to LHC
We study single jet and prompt-photon inclusive hadroproduction with
multi-Regge kinematics invoking the hypothesis of parton Reggeization in
t-channel exchanges at high energy. In this approach, the leading contributions
are due to the fusion of two Reggeized gluons into a Yang-Mills gluon and the
annihilation of a Reggeized quark-antiquark pair into a photon, respectively.
Adopting the Kimber-Martin-Ryskin and Bluemlein prescription to derive
unintegrated gluon and quark distribution functions of the proton from their
collinear counterparts, for which we use the Martin-Roberts-Stirling-Thorne
set, we evaluate cross section distributions in transverse momentum (p_T) and
rapidity. Without adjusting any free parameters, we find good agreement with
measurements by the CDF and D0 Collaborations at the Tevatron and by the ATLAS
Collaboration at the LHC in the region 2p_T/sqrt{S} < 0.1, where sqrt{S} is the
hadronic c.m. energy.Comment: 25 pages, 12 figures, error estimation improved, minor changes to the
text, 4 references added, accepted for publication in Phys. Rev.
Top Quark Production and Decay at Next-to-leading Order in Annihilation
We study the effects of QCD corrections to the process above threshold. We
show how to treat consistently to the gluon radiation in
both the production and the decay of the top quarks, while maintaining all
angular correlations in the event. At this order there is an ambiguity in the
event reconstruction whenever a real gluon occurs in the final state. We study
the effects of this ambiguity on the top mass and helicity angle distributions.
For a top mass of 175 GeV and collider energy of 400 GeV the gluon radiation is
emitted predominantly in the decay of the top quarks.Comment: 44 pages, LaTex, 10 embedded postscript figures, tarred and uuencoded
in separate fil
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