4,506 research outputs found
Analysis and discussion of the recent W mass measurements
The ATLAS and CDF measurements of the W mass are compared discussing some
similarities and differences in the quoted systematic uncertainties.Comment: Talk given at the 52nd Rencontres de Moriond Electroweak Interactions
and Unified Theories (2017
About the rapidity and helicity distributions of the W bosons produced at LHC
bosons are produced at LHC from a forward-backward symmetric initial
state. Their decay to a charged lepton and a neutrino has a strong spin
analysing power. The combination of these effects results in characteristic
distributions of the pseudorapidity of the leptons decaying from and
of different helicity. This observation may open the possibility to
measure precisely the and rapidity distributions for the two
transverse polarisation states of bosons produced at small transverse
momentum.Comment: 8 pages, 5 figure
A critical point in the distribution of lepton energies from the decay of a spin-1 resonance
We consider a spin- resonance produced with an arbitrary spectrum of
velocities and decaying into a pair of massless leptons, and we study the
probability density function of the energy of the leptons in the laboratory
frame. A special case is represented by the production of bosons in
proton-proton collisions, for which the energy of the charged lepton from the
decaying can be measured with sufficient accuracy for a high-precision
measurement of . We find that half of the resonance mass is a special
value of the lepton energy, since the probability density function at this
point is in general not analytic for a narrow-width resonance. In particular,
the higher-order derivatives of the density function are likely to develop
singularities, such as cusps or poles. A finite width of the resonance restores
the regularity, for example by smearing cusps and poles into local stationary
points. The quest for such points offers a handle to estimate the resonance
mass with much reduced dependence on the underlying production and decay
dynamics of the resonance.Comment: Revised version, 24 pages, 7 figure
Study the effect of beam energy spread and detector resolution on the search for Higgs boson decays to invisible particles at a future ee circular collider
We study the expected sensitivity to measure the branching ratio of Higgs
boson decays to invisible particles at a future circular \epem collider
(FCC-ee) in the process with ( or
) using an integrated luminosity of 3.5 ab at a center-of-mass
energy GeV. The impact of the energy spread of the FCC-ee beam
and of the resolution in the reconstruction of the leptons is discussed. %Two
different detector concepts are considered: a detector corresponding to the CMS
reconstruction performances and the expected design of the ILC detector. The
minimum branching ratio for a observation after 3.5ab of data
taking is . The branching ratio exclusion limit at
95\% CL is .Comment: 17 pages, submitted to EPJ
Impact of the PDFs on the Z and W lineshapes at LHC
The parton distribution functions (PDFs) of the proton play a role in
determining the lineshape of and bosons produced at the LHC. In
particular, the mode of the gauge boson virtuality is shifted with respect to
the pole due to the dependence of the partonic luminosity on the boson
virtuality. The knowledge of this shift contributes to the systematic
uncertainty for a direct measurement of the boson mass. A detailed study of the
shift and of its systematic uncertainty due to the limited knowledge of the
PDFs is obtained using a tree-level model of and boson production in
proton-proton collisions at TeV. A Monte Carlo simulation is
further used to validate the tree-level model and study the dependence of the
shift on the transverse momentum of the gauge bosons. The tree-level
calculation is found to provide a good description of the shift. The systematic
uncertainty on the lineshape due to the PDFs is estimated to be below one MeV
in the phase-space relevant for a future high-precision mass measurement of the
gauge boson masses at the LHC
Understanding the TeV Scale through LHC Data, Dark Matter and Other Experiments
The workshop focused on new data from the LHC after the completion of its initial 7 TeV run, providing an opportunity to interpret the results and to plan for the future 14 TeV run. Particular attention was paid to the first serious indications for the discovery of a Higgs boson at a mass of 125 GeV. In addition to hearing from LHC experimentalists, attention was also given to input from experimenters at the Tevatron, as well as to the direct and indirect detection of dark matter, flavor physics, and other related searches. The main characteristic of the workshop was the close collaboration and intensive debate between theorists and experimentalists. The workshop also hosted a conference, jointly with the Johns Hopkins Series, on October 16/19, 2012
Precise measurement of the W-boson mass with the CDF II detector
We have measured the W-boson mass MW using data corresponding to 2.2/fb of
integrated luminosity collected in proton-antiproton collisions at 1.96 TeV
with the CDF II detector at the Fermilab Tevatron collider. Samples consisting
of 470126 W->enu candidates and 624708 W->munu candidates yield the measurement
MW = 80387 +- 12 (stat) +- 15 (syst) = 80387 +- 19 MeV. This is the most
precise measurement of the W-boson mass to date and significantly exceeds the
precision of all previous measurements combined
Performance of CMS muon reconstruction in pp collision events at sqrt(s) = 7 TeV
The performance of muon reconstruction, identification, and triggering in CMS
has been studied using 40 inverse picobarns of data collected in pp collisions
at sqrt(s) = 7 TeV at the LHC in 2010. A few benchmark sets of selection
criteria covering a wide range of physics analysis needs have been examined.
For all considered selections, the efficiency to reconstruct and identify a
muon with a transverse momentum pT larger than a few GeV is above 95% over the
whole region of pseudorapidity covered by the CMS muon system, abs(eta) < 2.4,
while the probability to misidentify a hadron as a muon is well below 1%. The
efficiency to trigger on single muons with pT above a few GeV is higher than
90% over the full eta range, and typically substantially better. The overall
momentum scale is measured to a precision of 0.2% with muons from Z decays. The
transverse momentum resolution varies from 1% to 6% depending on pseudorapidity
for muons with pT below 100 GeV and, using cosmic rays, it is shown to be
better than 10% in the central region up to pT = 1 TeV. Observed distributions
of all quantities are well reproduced by the Monte Carlo simulation.Comment: Replaced with published version. Added journal reference and DO
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