3,716 research outputs found
Lepton flavor conserving Z -> l^+ l^-$ decays in the general two Higgs doublet model
We calculate the new physics effects to the branching ratios of the lepton
flavor conserving decays Z -> l^+ l^- in the framework of the general two Higgs
Doublet model. We predict the upper limits for the couplings
|\bar{\xi}^{D}_{N,\mu\tau}| and |\bar{\xi}^{D}_{N,\tau\tau}| as 3\times 10^2
GeV and 1\times 10^2 GeV, respectively.Comment: 9 pages, 3 figure
Picosecond laser-pump, x-ray probe spectroscopy of GaAs
A laser-pump, x-ray probe spectroscopic experiment is described, and the results are shown. The Ga KαKα x-ray fluorescence following x-ray absorption, at the Ga K absorption edge was measured, and its increase due to excitation with subpicosecond pulses of laser light at 4.6 eV photon energy was determined. The x-ray absorption, and thus the fluorescence, is increased for about 200 ps after the laser pulse because additional final states for the x-ray absorption are cleared in the valence band by the laser excitation. The technique could eventually lead to a femtosecond pump-probe spectroscopy with an absolute reference energy level and also to a femtosecond x-ray detector. This is of particular importance to future short-pulse x-ray sources, such as free-electron lasers. © 2002 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69690/2/RSINAK-73-12-4150-1.pd
Time-Shift in the OPERA set-up: proof against superluminal neutrinos without the need of knowing the CERN-LNGS distance and Reminiscences on the origin of the Gran Sasso Lab, of the 3rd neutrino and of the "Teramo Anomaly"
The LVD time stability allows to establish a time-shift in the OPERA
experiment, thus providing the first proof against Superluminal neutrinos,
using the horizontal muons of the "Teramo Anomaly". This proof is particularly
interesting since does not need the knowledge of the distance between the place
where the neutrinos are produced (CERN) and the place where they are detected
(LNGS). Since the Superluminal neutrinos generated in the physics community a
vivid interest in good and bad behaviour in physics research, the author
thought it was appropriate to recall the origin of the Gran Sasso Lab, of the
3rd neutrino, of the horizontal muons due to the "Teramo Anomaly" and of the
oscillation between leptonic flavours, when the CERN-Gran Sasso neutrino beam
was included in the project for the most powerful underground Laboratory in the
world.Comment: 35 pages, 25 Figures, Invited paper at the Gran Sasso mini-Workshop
on LNGS results on the neutrino velocity topic, Gran Sasso, Italy, 28 March
201
Like Sign Dilepton Signature for R-Parity Violating SUSY Search at the Tevatron Collider
The like sign dileptons provide the most promising signature for
superparticle search in a large category of -parity violating SUSY models.
We estimate the like sign dilepton signals at the Tevatron collider, predicted
by these models, over a wide region of the MSSM parameter space. One expects an
unambiguous signal upto a gluino mass of GeV ( GeV) with
the present (proposed) accumulated luminosity of .Comment: 12 page LaTeX file; 5 figures available upon request from the autho
Intermittency and Exotic Channels
It is pointed out that accurate measurements of short-range two-particle
correlations in like-charge and in channels should be
very helpful in determining the origin of the \lq\lq intermittency\rq\rq\
phenomenon observed recently for the like-charge pion pairs.Comment: 5 p., plain tex, preprint T94/078(Saclay), LPTHE 94/58(Orsay
On Neutrino Masses and Family Replication
The old issue of why there are more than one family of quarks and leptons is
reinvestigated with an eye towards the use of anomaly as a tool for
constraining the number of families. It is found that, by assuming the
existence of right-handed neutrinos (which would imply that neutrinos will have
a mass) and a new chiral SU(2) gauge theory, strong constraints on the number
of families can be obtained. In addition, a model, based on that extra SU(2),
is constructed where it is natural to have one "very heavy" fourth neutrino and
three almost degenerate light neutrinos whose masses are all of the Dirac type.Comment: RevTex, 12 pages with 1 figure, minor changes to the text and added
acknowledgment
Proton-antiproton annihilation into massive leptons
We extend previous calculations of polarization observables for the
annihilation reaction to the case of heavy
leptons, such as the -lepton. We consider the case when the beam and/or
the target are polarized, as well as the polarization of the outgoing leptons.
We give the dependence of the unpolarized cross section, angular asymmetry, and
various polarization observables on the relevant kinematical variables in the
center of mass and in the laboratory system, with particular attention to the
effect of the mass induced terms.Comment: 25 pages, 8 figure
Picosecond time-resolved x-ray diffraction probe of coherent lattice dynamics (abstract) (invited)
The short pulses of hard x rays from synchrotron and laser based sources are sensitive probes of lattice dynamics on an ultrafast time scale. Using pump–probe time-resolved x-ray diffraction, we are able to follow the propagation of a picosecond coherent acoustic pulse in an ultrafast laser-strained single crystal. Comparison of the data with dynamical diffraction simulations allows for the quantitative determination of both the surface and bulk components of the associated strain. This technique is scalable to femtosecond and shorter time scales as x-ray pulses become shorter in duration, such as in fourth generation light sources. In addition, the diffraction of x rays off of coherent optical phonons may lead to the production of a femtosecond x-ray switch. © 2002 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69893/2/RSINAK-73-3-1361-1.pd
Production, Decay, and Polarization of Excited Heavy Hadrons
We discuss the production via fragmentation of excited heavy mesons and
baryons, and their subsequent decay. In particular, we consider the question of
whether a net polarization of the initial heavy quark may be detected, either
in a polarization of the final ground state or in anisotropies in the decay
products of the excited hadron. The result hinges in part on a nonperturbative
parameter which measures the net transverse alignment of the light degrees of
freedom in the fragmentation process. We use existing data on charmed mesons to
extract this quantity for certain excited mesons. Using this result, we
estimate the polarization retention of charm and bottom baryons.Comment: 37 pages, 3 figures available upon request, uses phyzzx forma
Signals for Vector Leptoquarks in Hadronic Collisions
We analyze systematically the signatures of vector leptoquarks in hadronic
collisions. We examine their single and pair productions, as well as their
effects on the production of lepton pairs. Our results indicate that a machine
like the CERN Large Hadron Collider (LHC) will be able to unravel the existence
of vector leptoquarks with masses up to the range of -- TeV.Comment: 15 pages and 5 figures (available upon request or through anonymous
ftp), revtex3, IFUSP-P 108
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