4,784 research outputs found
Phenomenology of the minimal B-L extension of the Standard Model
We present the Large Hadron Collider (LHC) discovery potential in the
and heavy neutrino sectors of a enlarged Standard Model also
encompassing three heavy Majorana neutrinos. This model exhibits novel
signatures at the LHC, the most interesting arising from a decay chain
involving heavy neutrinos, eventually decaying into leptons and jets. In
particular, this signature allows one to measure the and heavy neutrino
masses involved. In addition, over a large region of parameter space, the heavy
neutrinos are rather long-lived particles producing distinctive displaced
vertices that can be seen in the detectors. Lastly, the simultaneous
measurement of both the heavy neutrino mass and decay length enables an
estimate of the absolute mass of the parent light neutrino. For completeness,
we will also compare the LHC and a future Linear Collider (LC) discovery
potentials.Comment: 4 pages, no figures. LaTeX. Talk given at "The 2009 Europhysics
Conference on High Energy Physics", Krakow, Poland, July 16-22, 200
Exploring Sensitivity to NMSSM Signatures with Low Missing Transverse Energy at the LHC
We examine scenarios in the Next-to-Minimal Supersymmetric Standard Model
(NMSSM), where pair-produced squarks and gluinos decay via two cascades, each
ending in a stable neutralino as Lightest Supersymmetric Particle (LSP) and a
Standard Model (SM)-like Higgs boson, with mass spectra such that the missing
transverse energy, , is very small. Performing
two-dimensional parameter scans and focusing on the hadronic decay giving a final state
we explore the sensitivity of a current LHC general-purpose
jets+ analysis to such scenarios.Comment: 17 pages, 17 figures, 6 table
Averaging lifetimes for B hadron species
The measurement of the lifetimes of the individual B species are of great interest. Many of these measurements are well below the 10 level of precision. However, in order to reach the precision necessary to test the current theoretical predictions, the results from different experiments need to be averaged. Therefore, the relevant systematic uncertainties of each measurement need to be well defined in order to understand the correlations between the results from different experiments. \par In this paper we discuss the dominant sources of systematic errors which lead to correlations between the different measurements. We point out problems connected with the conventional approach of combining lifetime data and discuss methods which overcome these problems
Les Houches 2011: Physics at TeV Colliders New Physics Working Group Report
We present the activities of the "New Physics" working group for the "Physics
at TeV Colliders" workshop (Les Houches, France, 30 May-17 June, 2011). Our
report includes new agreements on formats for interfaces between computational
tools, new tool developments, important signatures for searches at the LHC,
recommendations for presentation of LHC search results, as well as additional
phenomenological studies.Comment: 243 pages, report of the Les Houches 2011 New Physics Group; fix
three figure
Bose-Einstein Correlations in e+e- to W+W- at 172 and 183 GeV
Bose-Einstein correlations between like-charge pions are studied in hadronic
final states produced by e+e- annihilations at center-of-mass energies of 172
and 183 GeV. Three event samples are studied, each dominated by one of the
processes W+W- to qqlnu, W+W- to qqqq, or (Z/g)* to qq. After demonstrating the
existence of Bose-Einstein correlations in W decays, an attempt is made to
determine Bose-Einstein correlations for pions originating from the same W
boson and from different W bosons, as well as for pions from (Z/g)* to qq
events. The following results are obtained for the individual chaoticity
parameters lambda assuming a common source radius R: lambda_same = 0.63 +- 0.19
+- 0.14, lambda_diff = 0.22 +- 0.53 +- 0.14, lambda_Z = 0.47 +- 0.11 +- 0.08, R
= 0.92 +- 0.09 +- 0.09. In each case, the first error is statistical and the
second is systematic. At the current level of statistical precision it is not
established whether Bose-Einstein correlations, between pions from different W
bosons exist or not.Comment: 24 pages, LaTeX, including 6 eps figures, submitted to European
Physical Journal
Measurement of triple gauge boson couplings from WW production at LEP energies up to 189 GeV
A measurement of triple gauge boson couplings is presented, based on W-pair
data recorded by the OPAL detector at LEP during 1998 at a centre-of-mass
energy of 189 GeV with an integrated luminosity of 183 pb^-1. After combining
with our previous measurements at centre-of-mass energies of 161-183 GeV we
obtain k_g=0.97 +0.20 -0.16, g_1^z=0.991 +0.060 -0.057 and lambda_g=-0.110
+0.058 -0.055, where the errors include both statistical and systematic
uncertainties and each coupling is determined by setting the other two
couplings to their SM values. These results are consistent with the Standard
Model expectations.Comment: 28 pages, 8 figures, submitted to Eur. Phys. J.
Search for Yukawa Production of a Light Neutral Higgs Boson at LEP
Within a Two-Higgs-Doublet Model (2HDM) a search for a light Higgs boson in
the mass range of 4-12 GeV has been performed in the Yukawa process e+e- -> b
bbar A/h -> b bbar tau+tau-, using the data collected by the OPAL detector at
LEP between 1992 and 1995 in e+e- collisions at about 91 GeV centre-of-mass
energy. A likelihood selection is applied to separate background and signal.
The number of observed events is in good agreement with the expected
background. Within a CP-conserving 2HDM type II model the cross-section for
Yukawa production depends on xiAd = |tan beta| and xihd = |sin alpha/cos beta|
for the production of the CP-odd A and the CP-even h, respectively, where tan
beta is the ratio of the vacuum expectation values of the Higgs doublets and
alpha is the mixing angle between the neutral CP-even Higgs bosons. From our
data 95% C.L. upper limits are derived for xiAd within the range of 8.5 to 13.6
and for xihd between 8.2 to 13.7, depending on the mass of the Higgs boson,
assuming a branching fraction into tau+tau- of 100%. An interpretation of the
limits within a 2HDM type II model with Standard Model particle content is
given. These results impose constraints on several models that have been
proposed to explain the recent BNL measurement of the muon anomalous magnetic
moment.Comment: 24 pages, 9 figures, Submitted to Euro. Phys. J.
Search for the Standard Model Higgs Boson with the OPAL Detector at LEP
This paper summarises the search for the Standard Model Higgs boson in e+e-
collisions at centre-of-mass energies up to 209 GeV performed by the OPAL
Collaboration at LEP. The consistency of the data with the background
hypothesis and various Higgs boson mass hypotheses is examined. No indication
of a signal is found in the data and a lower bound of 112.7GeV/C^2 is obtained
on the mass of the Standard Model Higgs boson at the 95% CL.Comment: 51 pages, 21 figure
- …