1,916 research outputs found
A Fresh Look at Gauge Coupling Unification
The apparent unification of gauge couplings around 10^16 GeV is one of the
strong arguments in favor of Supersymmetric extensions of the Standard Model
(SM). In this contribution a new analysis, using the latest experimental data,
is performed. The strong coupling alpha_s emerges as the key factor for
evaluating the results of the fits, as the experimental and theoretical
uncertainties in its measurements are substantially higher than for the
electromagnetic and weak couplings. The present analysis pays special attention
to numerical and statistical details. The results, combined with the current
limits on the supersymmetric particle masses, favor a value for the SUSY scale
<~ 150 GeV and for alpha_s = 0.118-0.119.Comment: 4 pages, 1 table, 1 figure; presented at the Meeting of the Division
of Particles and Fields of the APS, Riverside, USA, August 200
Study of Parton Density Function Uncertainties with LHAPDF and PYTHIA at LHC
The experimental errors in current and future hadron colliders are expected
to decrease to a level that will challenge the uncertainties in the theoretical
calculations. One important component in the prediction uncertainties comes
from the Parton Density Functions of the (anti)proton. In this work we develop
an interface from the Les Houches Accord Parton Density Functions (LHAPDF)
package to the very popular Monte Carlo generator {\tt PYTHIA} version 6.2.
Then we proceed to estimate the PDF uncertainties for the production of
Drell-Yan pairs from the Z pole to masses above 1 \TeV and for Higgs bosons
at LHC. The measurement of the electro-weak mixing angle at LHC as a
particularly difficult case is studied.Comment: 8 pages, 5 tables; code available on request from the author;
Contribution to LHC / LC Study Group Working Documen
Other BSM Searches at the LHC
A review of the discovery potential of LHC for new phenomena beyond the
Standard Model (BSM) other than Supersymmetry in the early phase of running is
presented. Topics covered include searches for extra dimensions in different
scenarios (ADD, Randall-Sundrum, black holes ...), resonance hunting in
di-lepton, di-photon and di-jet final states, searches for contact
interactions, heavy stable charged particles, technicolor, etc. The strategies
of the ATLAS and CMS experiments to understand the detectors and prepare them
for "search" mode and the prospects for discoveries using early data are
described.Comment: 9 pages, 11 figures, Invited LHC review talk at HCP2008, 19th Hadron
Collider Physics Symposium 2008, Galena, IL, USA, May 27-31 200
Strong Coupling Running, Gauge Coupling Unification and the Scale of New Physics
The apparent unification of gauge couplings in Grand Unified Theories around
10 GeV is one of the strong arguments in favor of Supersymmetric
extensions of the Standard Model. In this paper, an analysis of the
measurements of the strong coupling running from the CMS experiment at the LHC
is combined with a "traditional" gauge coupling unification analysis using data
at the Z peak. This approach places powerful constraints on the possible scales
of new physics and on the parameters around the unification scale. A
supersymmetric analysis without GUT threshold corrections describes the CMS
data well and provides perfect unification. The favored scales are $M_{SUSY}\
=\ 2820\ +670\ -540M_{GUT}\ =\ 1.05 \pm 0.06 \cdot 10^{16}$ GeV. For
zero or small threshold corrections the scale of new physics may be well within
LHC reach.Comment: 11 pages, 4 figures, 2 table
Sensitivity to Contact Interactions and Extra Dimensions in Di-lepton and Di-photon Channels at Future Colliders
Virtual effects from a generic description of physics beyond the Standard
Model in terms of contact interactions, or from large extra dimensions will
modify the observed cross sections for easy to detect final states like lepton
or photon pairs, and can be used to probe scales much higher than the
center-of-mass energy of the partons initiating the interactions. In this note
the sensitivity reach of the Large Hadron Collider to contact interactions in
the Drell-Yan channels and of a Future Linear Collider to contact interactions
and extra dimensions in , and final states
are studied. Experimental aspects of the measurements, systematic error effects
and the evolution of the search reach with accumulated luminosity are
considered.Comment: 13 pages, 2 figures, 8 tables; Contribution to LHC / LC Study Group
Working Documen
Gauge Coupling Unification, SUSY Scale and Strong Coupling Running
The apparent unification of gauge couplings around 10^16 GeV is one of the
strong arguments in favor of Supersymmetric extensions of the Standard Model
(SM). In this contribution two new analyses of the gauge coupling running, the
latter using in contrast to previous studies not data at the Z peak but at LEP2
energies, are presented. The generic SUSY scale in the more precise novel
approach is 93 < M_SUSY < 183 GeV, easily within LHC, and possibly even within
Tevatron reach.Comment: 3 pages, 1 table, 2 figures; presented at PANIC05, Particles and
Nuclei International Conference, Santa Fe, New Mexico, October 24-28, 200
Fermion-pair Production above the Z and Search for New Phenomena
A review of the measurements of hadron, flavour-tagged and lepton-pair
production cross-sections and lepton-pair forward-backward asymmetries
performed by the four LEP experiments ALEPH, DELPHI, L3 and OPAL at energies
between 130 and 183 GeV is given. All 183 GeV results are preliminary. The
searches by the four collaborations for new physics phenomena like contact
interactions and compositeness, exchange of R-parity violating sneutrinos or
squarks, leptoquarks or additional heavy gauge bosons Z' are summarized. No
evidence for deviations from the Standard Model expectations is found and new
or improved limits are derived.Comment: 6 pages, 3 figures, 2 tables, presented at the XXXIInd Rencontres de
Moriond, Electroweak Interactions and Unified Theories, Les Arcs, France,
March 14-21, 199
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