6,821 research outputs found
Multiplicities, fluctuations and correlations
The recent results on hadron multiplicities in heavy and light quark
fragmentation, multiplicity local fluctuations and multiparticle correlations
submitted to the Conference are reviewed.Comment: 5 pages, 4 eps figs. Talk given at the 31st International Conference
on High Energy Physics (ICHEP02), Amsterdam, The Netherlands, 24-31 July
2002. To appear in the Proceeding
Running of the QED coupling in small-angle Bhabha scattering at LEP
Using the OPAL detector at LEP, the running of the effective QED coupling
alpha(t) is measured for space-like momentum transfer, 2 \leq -t \leq 6 GeV^2,
from the angular distribution of small-angle Bhabha scattering. This is
currently the most significant direct observation of the running of the QED
coupling in a single experiment and the first clear evidence of the hadronic
contribution to the running in the space-like region. Our result is in good
agreement with standard evaluations of alpha(t), based on data in the time-like
region.Comment: Talks given at the 19th Rencontres De Physique De La Vallee D'Aoste
(27.2-5.3.05), La Thuile, Italy and at the 40th Rencontres De Moriond On
Electroweak Interactions And Unified Theories (5.3-12.3.05), La Thuile,
Italy. Added 1 figure and related text wrt vers.
The CMS muon system in Run2: preparation, status and first results
The CMS muon system has played a key role for many physics results obtained
from the LHC Run-1 data. During the Long Shutdown (2013-2014) significant
upgrades have been carried out on the muon detectors and on the L1 muon
trigger. In parallel the algorithms for muon reconstruction and identification
have been improved for both the High-Level Trigger and the offline
reconstruction. Results of studies performed on data and Monte Carlo
simulations will be presented, with focus on the improvements aiming to ensure
an excellent performance in conditions of multiplicity of pileup events and
bunch spacing expected during the high-luminosity phase of Run-2. The early
muon performance results from LHC Run-2 will be shown.Comment: 8 pages, 13 figures, to be published in the proceedings of EPS-HEP
201
Fermion pair production at LEP2 and interpretations
Preliminary results on , ,
including all LEP2 data are discussed. Good agreement is found with the
Standard Model up to the highest energies. Limits on possible new physics are
extracted.Comment: 8 pages, 4 figures, to appear in the Proceedings of the New Trends in
High-Energy Physics, Yalta, Ukraine, September 22 - 29, 200
A Framework to Simultaneously Explain Tiny Neutrino Mass and Huge Missing Mass Problem of the Universe
Recently a minimalistic scenario has been developed to explain dark matter
and tiny but nonzero neutrino masses. In this scenario, a new scalar called
SLIM plays the role of the dark matter. Neutrinos achieve Majorana mass through
a one-loop diagram. This scenario can be realized for both real and complex
SLIM. Simultaneously explaining the neutrino mass and dark matter abundance
constrains the scenario. In particular for real SLIM, an upper bound of a few
MeV on the masses of the new particles and a lower bound on their coupling are
obtained which make the scenario testable. The low energy scenario can be
embedded within various symmetric models. I shall briefly
review the scenario and a specific model that embeds the scenario, with special
emphasis on the effects in the charged Kaon decay which might be observable at
the KLOE and NA62 experiments.Comment: 7 pages, 1 figur
Quark mixing and CP violation - the CKM matrix
I present the status of the elements and parameters of the
Cabibbo-Kobayashi-Maskawa (CKM) matrix and summarise the related theoretical
progress since "Lepton-Photon 2003". One finds |V_{us}| = 0.2227 +/- 0.0017
from K and tau decays and |V_{cb}| = (41.6 +/- 0.5) * 10^{-3} from inclusive
semileptonic B decays. The unitarity triangle can now be determined from
tree-level quantities alone and the result agrees well with the global fit
including flavour-changing neutral current (FCNC) processes, which are
sensitive to new physics. From the global fit one finds the three CKM angles
theta_{12}=12.9 +/- 0.1 degrees, theta_{23}= 2.38 +/- 0.03 degrees and
theta_{13}= 0.223 +/- 0.007 degrees in the standard PDG convention. The CP
phase equals delta_{13} = gamma = (58.8 +5.3/-5.8) degrees at 1 sigma CL and
gamma=(58.8 +11.2/-15.4) degrees at 2 sigma CL. A major progress are first
results from fully unquenched lattice QCD computations for the hadronic
quantities entering the UT fit. I further present the calculation of three-loop
QCD corrections to the charm contribution in K+ -> pi+ nu nu-bar decays, which
removes the last relevant theoretical uncertainty from the K -> pi nu nu-bar
system. Finally I discuss mixing-induced CP asymmetries in b -> s q-bar q
penguin decays, whose naive average is below its Standard Model value by 3
sigma.Comment: 14 pages, 12 figures, plenary talk at "Lepton-Photon 2005
Does the hard pomeron obey Regge factorisation?
While data for the proton structure function demand the presence of a
hard-pomeron contribution even at quite small Q^2, previous fits to the pp and
p\bar p total cross sections have found that in these there is little or no
room for such a contribution. We re-analyse the data and show that itmay indeed
be present and that, further, it probably obeys Regge factorisation:
sigma^{gamma p}(s,Q_1^2)sigma^{gamma p}(s,Q_2^2)= sigma^{pp}(s)sigma^{gamma
gamma}(s,Q_1^2,Q_2^2) for all values of Q_1^2 and Q_2^2.Comment: 11 pages, 10 figure
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