44 research outputs found
Phenomenological analysis connecting proton-proton and antiproton-proton elastic scattering
Based on the behavior of the elastic scattering data, we introduce an almost
model-independent parametrization for the imaginary part of the scattering
amplitude, with the energy and momentum transfer dependences inferred on
empirical basis and selected by rigorous theorems and bounds from axiomatic
quantum field theory. The corresponding real part is analytically evaluated by
means of dispersion relations, allowing connections between particle-particle
and particle-antiparticle scattering. Simultaneous fits to proton-proton and
antiproton-proton experimental data in the forward direction and also including
data beyond the forward direction, lead to a predictive formalism in both
energy and momentum transfer. We compare our extrapolations with predictions
from some popular models and discuss the applicability of the results in the
normalization of elastic rates that can be extracted from present and future
accelerator experiments (Tevatron, RHIC and LHC).Comment: 17 pages, 17 figures, to appear in Eur. Phys. J.
Photon and Z induced heavy charged lepton pair production at a hadron supercollider
We investigate the pair production of charged heavy leptons via
photon-induced processes at the proposed CERN Large Hadron Collider (LHC).
Using effective photon and Z approximations, rates are given for
production due to fusion and fusion for the cases of
inelastic, elastic and semi-elastic collisions. These are compared with
the corresponding rates for production via the gluon fusion and Drell-Yan
mechanisms. Various and differential luminosities
for collisions are also presented.Comment: 22 pages, RevTex 3.0, 6 uuencoded and compressed postscript figures
included. Reference to one paper changed from the original preprint number to
the published version. Everything else unchange
Relic Neutrino Absorption Spectroscopy
Resonant annihilation of extremely high-energy cosmic neutrinos on big-bang
relic anti-neutrinos (and vice versa) into Z-bosons leads to sizable absorption
dips in the neutrino flux to be observed at Earth. The high-energy edges of
these dips are fixed, via the resonance energies, by the neutrino masses alone.
Their depths are determined by the cosmic neutrino background density, by the
cosmological parameters determining the expansion rate of the universe, and by
the large redshift history of the cosmic neutrino sources. We investigate the
possibility of determining the existence of the cosmic neutrino background
within the next decade from a measurement of these absorption dips in the
neutrino flux. As a by-product, we study the prospects to infer the absolute
neutrino mass scale. We find that, with the presently planned neutrino
detectors (ANITA, Auger, EUSO, OWL, RICE, and SalSA) operating in the relevant
energy regime above 10^{21} eV, relic neutrino absorption spectroscopy becomes
a realistic possibility. It requires, however, the existence of extremely
powerful neutrino sources, which should be opaque to nucleons and high-energy
photons to evade present constraints. Furthermore, the neutrino mass spectrum
must be quasi-degenerate to optimize the dip, which implies m_{nu} >~ 0.1 eV
for the lightest neutrino. With a second generation of neutrino detectors,
these demanding requirements can be relaxed considerably.Comment: 19 pages, 26 figures, REVTeX
Three-generation flavor transitions and decays of supernova relic neutrinos
If neutrinos have mass, they can also decay. Decay lifetimes of cosmological
interest can be probed, in principle, through the detection of the redshifted,
diffuse neutrino flux produced by all past supernovae--the so-called supernova
relic neutrino (SRN) flux. In this work, we solve the SRN kinetic equations in
the general case of three-generation flavor transitions followed by invisible
(nonradiative) two-body decays. We then use the general solution to calculate
observable SRN spectra in some representative decay scenarios. It is shown
that, in the presence of decay, the SRN event rate can basically span the whole
range below the current experimental upper bound--a range accessible to future
experimental projects. Radiative SRN decays are also briefly discussed.Comment: 25 pages, including 7 figure
Heavy quarkonium: progress, puzzles, and opportunities
A golden age for heavy quarkonium physics dawned a decade ago, initiated by
the confluence of exciting advances in quantum chromodynamics (QCD) and an
explosion of related experimental activity. The early years of this period were
chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in
2004, which presented a comprehensive review of the status of the field at that
time and provided specific recommendations for further progress. However, the
broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles
could only be partially anticipated. Since the release of the YR, the BESII
program concluded only to give birth to BESIII; the -factories and CLEO-c
flourished; quarkonium production and polarization measurements at HERA and the
Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the
deconfinement regime. All these experiments leave legacies of quality,
precision, and unsolved mysteries for quarkonium physics, and therefore beg for
continuing investigations. The plethora of newly-found quarkonium-like states
unleashed a flood of theoretical investigations into new forms of matter such
as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the
spectroscopy, decays, production, and in-medium behavior of c\bar{c}, b\bar{b},
and b\bar{c} bound states have been shown to validate some theoretical
approaches to QCD and highlight lack of quantitative success for others. The
intriguing details of quarkonium suppression in heavy-ion collisions that have
emerged from RHIC have elevated the importance of separating hot- and
cold-nuclear-matter effects in quark-gluon plasma studies. This review
systematically addresses all these matters and concludes by prioritizing
directions for ongoing and future efforts.Comment: 182 pages, 112 figures. Editors: N. Brambilla, S. Eidelman, B. K.
Heltsley, R. Vogt. Section Coordinators: G. T. Bodwin, E. Eichten, A. D.
Frawley, A. B. Meyer, R. E. Mitchell, V. Papadimitriou, P. Petreczky, A. A.
Petrov, P. Robbe, A. Vair
Model-independent analysis of Higgs spin and CP properties in the process
In this paper we investigate methods to study the Higgs coupling.
The spin and CP properties of a Higgs boson are analysed in a model-independent
way in its associated production with a pair in high-energy
collisions. We study the prospects of establishing the CP quantum numbers of
the Higgs boson in the CP-conserving case as well as those of determining the
CP-mixing if CP is violated. We explore in this analysis the combined use of
the total cross section and its energy dependence, the polarisation asymmetry
of the top quark and the up-down asymmetry of the antitop with respect to the
top-electron plane. We find that combining all three observables remarkably
reduces the error on the determination of the CP properties of the Higgs Yukawa
coupling. Furthermore, the top polarisation asymmetry and the ratio of cross
sections at different collider energies are shown to be sensitive to the spin
of the particle produced in association with the top quark pair
QCD Corrections and Non-standard Three Vector Boson Couplings in Production at Hadron Colliders
The process p\,p\hskip-7pt\hbox{^{^{(\!-\!)}}} \rightarrow W^{+} W^{-} + X
\rightarrow \ell^+_1 \nu_1 \ell^-_2 \bar \nu_2 + X is calculated to for general and conserving couplings (). The prospects for probing the couplings in this reaction are
explored. The impact of QCD corrections and various
background processes on the observability of non-standard couplings in
production at the Tevatron and the Large Hadron Collider (LHC) is
discussed in detail. Sensitivity limits for anomalous couplings are
derived at next-to-leading order for the Tevatron and LHC center of mass
energies, and are compared to the bounds which can be achieved in other
processes. Unless a jet veto or a cut on the total transverse momentum of the
hadrons in the event is imposed, the QCD corrections and
the background from top quark production decrease the sensitivity of
p\,p\hskip-7pt\hbox{^{^{(\!-\!)}}} \rightarrow W^{+} W^{-} + X \rightarrow
\ell^+_1 \nu_1 \ell^-_2 \bar \nu_2 + X to anomalous couplings by a
factor two to five.Comment: REVTEX 3, 62 pages, 21 Figures (not included available upon request),
the postscript file of the complete paper is available at
ftp://ucdhep.ucdavis.edu/han/ww/ww_paper.p
Search for leptophobic Z ' bosons decaying into four-lepton final states in proton-proton collisions at root s=8 TeV
Peer reviewe
Search for heavy resonances decaying into a vector boson and a Higgs boson in final states with charged leptons, neutrinos, and b quarks
Peer reviewe