2,760 research outputs found
The role of energy-momentum conservation in emission of Cherenkov gluons
The famous formula for the emission angle of Cherenkov radiation should be
modified when applied to hadronic reactions because of recoil effects. They
impose the upper limit on the energy of the gluon emitted at a given angle.
Also, it leads to essential corrections to the nuclear refractive index value
as determined from the angular position of Cherenkov rings.Comment: 6
Laser cooling of electron beams for linear colliders
A novel method of electron beam cooling is considered which can be used for
linear colliders. The electron beam is cooled during collision with focused
powerful laser pulse. With reasonable laser parameters (laser flash energy
about 10 J) one can decrease transverse beam emittances by a factor about 10
per one stage. The ultimate transverse emittances are much below those
achievable by other methods. Beam depolarization during cooling is about 5--15
% for one stage. This method is especially useful for photon colliders and
opens new possibilities for e+e- colliders.Comment: 4 pages, Latex, v2 corresponds to the PRL paper with erratum (in
1998) include
Single Leptoquark Production at and Colliders
We consider single production of leptoquarks (LQ's) at and
colliders, for two values of the centre-of-mass energy,
GeV and 1 TeV. We find that LQ's which couple within the first
generation are observable for LQ masses almost up to the kinematic limit, both
at and colliders, for the LQ coupling strength equal to
. The cross sections for single production of - and
-generation LQ's at colliders are too small to be observable.
In collisions, on the other hand, -generation LQ's with
masses much larger than can be detected. However,
-generation LQ's can be seen at colliders only for
masses at most , making their observation more probable via the
pair production mechanism.Comment: plain TeX, 14 pages, 6 figures (not included but available on
request), some minor changes to the text, one reference added, figures and
conclusions unchanged, UdeM-LPN-TH-93-152, McGill-93/2
Differential operators and Cherednik algebras
We establish a link between two geometric approaches to the representation
theory of rational Cherednik algebras of type A: one based on a noncommutative
Proj construction, used in [GS]; the other involving quantum hamiltonian
reduction of an algebra of differential operators, used in [GG].
In the present paper, we combine these two points of view by showing that the
process of hamiltonian reduction intertwines a naturally defined geometric
twist functor on D-modules with the shift functor for the Cherednik algebra.
That enables us to give a direct and relatively short proof of the key result,
[GS, Theorem 1.4] without recourse to Haiman's deep results on the n! theorem.
We also show that the characteristic cycles defined independently in these two
approaches are equal, thereby confirming a conjecture from [GG].Comment: 37 p
On the origin of cosmic rays
Uniform and metagalactic cosmic ray models - halo, disk, and nonstationary galactic model
Charge asymmetry of pions in the process
The study of the charge asymmetry of produced particles allows to investigate
the interference of different production mechanisms and to determine new
features of the corresponding amplitudes. In the process the two-pion system is produced via two mechanisms: two-photon
(C-even state) and bremsstrahlung (C-odd state) production. We study the charge
asymmetry of pions in a differential in the pion momenta cross section
originating from an interference between these two mechanisms. At low effective
mass of dipions this asymmetry is directly related to the s- and p-phases of
elastic scattering. At higher energies it can give new information
about the meson family, meson, etc. The asymmetry is
expressed via the pion form factor and helicity amplitudes for
the subprocess as where we have calculated analytically the coefficients
for the region giving the main contribution to the effect. Several
distributions of pions are presented performing a numerical analysis in a model
with point-like pions. In the region near the dipion threshold the asymmetry is
of the order of 1%. We show that with suitable cuts the signal to background
ratio can be increased up to about 10%.Comment: 16 pages, 10 figures, LaTeX, style files for EPJC include
Full one-loop QCD and electroweak corrections to sfermion pair production in collisions
We have calculated the full one-loop electroweak (EW) and QCD corrections to
the third generation scalar-fermion pair production processes at an
electron-positron linear collider(LC) in the minimal supersymmetric standard
model (MSSM). We analyze the dependence of the radiative corrections on the
parameters such as the colliding energy and the SUSY
fundamental parameters , , , and so forth. The
numerical results show that the EW corrections to the squark-, stau-pair
production processes and QCD corrections to the squark-pair production
processes give substantial contributions in some parameter space. The EW
relative corrections to squark-pair production processes can be comparable with
QCD corrections at high energies. Therefore, these EW and QCD corrections
cannot be neglected in precise measurement of sfermion pair productions via
collision at future linear colliders.Comment: to be appeared in Phys. Rev.
Beam energy measurement at linear colliders using spin precession
Linear collider designs foresee some bends of about 5-10 mrad. The spin
precession angle of one TeV electrons on 10 mrad bend is 23.2 rad and it
changes proportional to the energy. Measurement of the spin direction using
Compton scattering of laser light on electrons before and after the bend allows
determining the beam energy with an accuracy about of 10^{-5}. In this paper
the principle of the method, the procedure of the measurement and possible
errors are discussed. Some remarks about importance of plasma focusing effects
in the method of beam energy measurement using Moller scattering are given.Comment: 7 pages, Latex, 4 figures(.eps). In v.3 corresponds to journal
publication. Talk at 26-th Advanced ICFA Beam Dynamic Workshop on
Nanometre-Size Colliding Beams (Nanobeam2002), Lausanne, Switzerland, Sept
2-6, 200
Ultimate parameters of the photon collider at the ILC
At linear colliders, the e+e- luminosity is limited by beam-collision
effects, which determine the required emittances of beams in damping rings
(DRs). While in gamma-gamma collisions at the photon collider, these effects
are absent, and so smaller emittances are desirable. In present damping rings
designs, nominal DR parameters correspond to those required for e+e-
collisions. In this note, I would like to stress once again that as soon as we
plan the photon-collider mode of ILC operation, the damping-ring emittances are
dictated by the photon-collider requirements--namely, they should be as small
as possible. This can be achieved by adding more wigglers to the DRs; the
incremental cost is easily justified by a considerable potential improvement of
the gamma-gamma luminosity. No expert analysis exists as of yet, but it seems
realistic to obtain a factor five increase of the gamma-gamma luminosity
compared to the ``nominal'' DR design.Comment: Talk at LCWS06, Bangalore, India, March 2006, to be published in
Indian Journal of Physics, 5 pp, Latex, 1 .eps figur
- …