853 research outputs found
Probabilistic Particle Flow Algorithm for High Occupancy Environment
Algorithms based on the particle flow approach are becoming increasingly
utilized in collider experiments due to their superior jet energy and missing
energy resolution compared to the traditional calorimeter-based measurements.
Such methods have been shown to work well in environments with low occupancy of
particles per unit of calorimeter granularity. However, at higher instantaneous
luminosity or in detectors with coarse calorimeter segmentation, the overlaps
of calorimeter energy deposits from charged and neutral particles significantly
complicate particle energy reconstruction, reducing the overall energy
resolution of the method. We present a technique designed to resolve
overlapping energy depositions of spatially close particles using a
statistically consistent probabilistic procedure. The technique is nearly free
of ad-hoc corrections, improves energy resolution, and provides new important
handles that can improve the sensitivity of physics analyses: the uncertainty
of the jet energy on an event-by-event basis and the estimate of the
probability of a given particle hypothesis for a given detector response. When
applied to the reconstruction of hadronic jets produced in the decays of tau
leptons using the CDF-II detector at Fermilab, the method has demonstrated
reliable and robust performance.Comment: Accepted by Nuclear Instruments and Methods
Independent measurement of the top quark mass and the light- and bottom-jet energy scales at hadron colliders
A method for the simultaneous determination of the energy scales for b-quark
jets and light jets, the jet energy resolution, and the top quark mass at
hadron colliders is presented. The method exploits the unique kinematics of
events with top-antitop pair production, where one of the top quarks involves a
leptonic and one a hadronic W boson decay. The paper shows a feasibility study
of how this simultaneous measurement can be performed at the upcoming LHC
experiments ATLAS and CMS.Comment: 10 pages, 5 figure
Search for B\u3csub\u3es\u3c/sub\u3e\u3csup\u3e0\u3c/sup\u3e→µ\u3csup\u3e+\u3c/sup\u3eµ\u3csup\u3e-\u3c/sup\u3e and B\u3csub\u3ed\u3c/sub\u3e\u3csup\u3e0\u3c/sup\u3e→µ\u3csup\u3e+\u3c/sup\u3eµ\u3csup\u3e-\u3c/sup\u3e Decays in \u3ci\u3ep\u3c/i\u3e\u3csup\u3eρ̅\u3c/sup\u3e Collisions with CDF II
We report on a search for Bs0→µ+µ- and Bd0→µ+µ- decays in pρ̅ collisions at √8=1.96 TeV using 364 pb-1 of data collected by the CDF II detector at the Fermilab Tevatron Collider. After applying all selection requirements, we observe no candidates inside the Bs0 or Bd0 mass windows. The resulting upper limits on the branching fractions are Ɓ (Bs0→µ+µ-)\u3c1.5×10-7 and Ɓ (Bd0→µ+µ-)\u3c3.9×10-8 at 90% confidence level
B(Ds^+ -> l^+ nu) and the Decay Constant f_(D_s^+)
I report final CLEO-c results on the purely leptonic decays of the D_s^+ ->
l^+ nu, for the cases when l^+ is a mu^+ or tau^+, when it decays into pi^+
anti-nu, using 314/pb of data at 4.170 GeV. I also include preliminary results
from the tau^+ -> e^+ nu anti-nu channel using 195/pb. Combining both we
measure f_{D_s}= 275 +/- 10 +/- 5 MeV, and f_{D_s^+}/{f_{D^+}=1.24 +/- 0.10 =/-
0.03 .Comment: Presented at "The 2007 Europhysics Conference on High Energy
Physics," Manchester, England, 19-25 July 2007, to appear in the proceedings.
Three pages, 1 figur
Review of Top Quark Physics Results
As the heaviest known fundamental particle, the top quark has taken a central
role in the study of fundamental interactions. Production of top quarks in
pairs provides an important probe of strong interactions. The top quark mass is
a key fundamental parameter which places a valuable constraint on the Higgs
boson mass and electroweak symmetry breaking. Observations of the relative
rates and kinematics of top quark final states constrain potential new physics.
In many cases, the tests available with study of the top quark are both
critical and unique. Large increases in data samples from the Fermilab Tevatron
have been coupled with major improvements in experimental techniques to produce
many new precision measurements of the top quark. The first direct evidence for
electroweak production of top quarks has been obtained, with a resulting direct
determination of . Several of the properties of the top quark have been
measured. Progress has also been made in obtaining improved limits on potential
anomalous production and decay mechanisms. This review presents an overview of
recent theoretical and experimental developments in this field. We also provide
a brief discussion of the implications for further efforts.Comment: 119 pages, 55 figure
Evidence for the Exclusive Decay \u3ci\u3eB\u3c/i\u3e\u3csub\u3e\u3ci\u3ec\u3c/i\u3e\u3c/sub\u3e\u3csup\u3e±\u3c/sup\u3e → \u3ci\u3eJ\u3c/i\u3e/ψπ\u3csup\u3e±\u3c/sup\u3e and Measurement of the Mass of the \u3ci\u3eB\u3c/i\u3e\u3csub\u3e\u3ci\u3ec\u3c/i\u3e\u3c/sub\u3e\u3csup\u3e±\u3c/sup\u3e Meson
We report the first evidence for a fully reconstructed decay mode of the Bc± meson in the channel Bc± → J/ψπ±, with J/ψ → μ+ μ-. The analysis is based on an integrated luminosity of 360 pb-1 in pp̅ collisions at 1.96 TeV center of mass energy collected by the Collider Detector at Fermilab. We observe 14.6 ± 4.6 signal events with a background of 7.1 ± 0.9 events, and a fit to the J/ ψπ± mass spectrum yields a Bc± mass of 6285.7 ± 5.3(stat) ± 1.2(syst) MeV/c2. The probability of a peak of this magnitude occurring by random fluctuation in the search region is estimated as 0.012%
Top-Quark Mass Measurement from Dilepton Events at CDF II
We report a measurement of the top-quark mass using events collected by the CDF II detector from pp̅ collisions at √s = 1.96 TeV at the Fermilab Tevatron. We calculate a likelihood function for the top-quark mass in events that are consistent with tt̅ → b̅ℓ-ν̅ℓbℓ′+ν′ℓ decays. The likelihood is formed as the convolution of the leading-order matrix element and detector resolution functions. The joint likelihood is the product of likelihoods for each of 33 events collected in 340 pb-1 of integrated luminosity, yielding a top-quark mass Mt = 165.2 ± 6.1(stat) ± 3.4(syst) GeV/c2. This first application of a matrix-element technique to tt̅ → bℓ+νℓb̅ℓ′-ν̅ℓ′ decays gives the most precise single measurement of Mt in dilepton events. Combined with other CDF run II measurements using dilepton events, we measure Mt = 167.9 ± 5.2(stat) ± 3.7(syst) GeV/c2
Measurement of heavy-flavour production in proton-proton collisions at sqrt{s} = 7 TeV with ALICE
The measurement of the heavy-flavour production cross sections in pp
collisions at the LHC will allow to test perturbative QCD calculations in a new
energy domain. Moreover, within the physics program of the ALICE experiment, it
will provide the reference for the study of medium effects in Pb-Pb collisions,
where heavy quarks are regarded as sensitive probes of parton-medium
interaction dynamics. We present the status and first preliminary results of
charm and beauty production measurements with the ALICE experiment, using
hadronic D meson decays and semi-leptonic D and B meson decays, including the
first cross section measurement of muons from heavy flavour decays at forward
rapidity. We also describe the preliminary cross section measurement for J/psi
production, obtained using the di-electron decay channel at central rapidity
and the di-muon decay channel at forward rapidity.Comment: 8 pages, 5 figures, proceedings of the conference HARD PROBES 2010,
Eilat, October 201
Search for B\u3csub\u3es\u3c/sub\u3e\u3csup\u3e0\u3c/sup\u3e→µ\u3csup\u3e+\u3c/sup\u3eµ\u3csup\u3e-\u3c/sup\u3e and B\u3csub\u3ed\u3c/sub\u3e\u3csup\u3e0\u3c/sup\u3e→µ\u3csup\u3e+\u3c/sup\u3eµ\u3csup\u3e-\u3c/sup\u3e Decays in \u3ci\u3ep\u3c/i\u3e\u3csup\u3eρ̅\u3c/sup\u3e Collisions with CDF II
We report on a search for Bs0→µ+µ- and Bd0→µ+µ- decays in pρ̅ collisions at √8=1.96 TeV using 364 pb-1 of data collected by the CDF II detector at the Fermilab Tevatron Collider. After applying all selection requirements, we observe no candidates inside the Bs0 or Bd0 mass windows. The resulting upper limits on the branching fractions are Ɓ (Bs0→µ+µ-)\u3c1.5×10-7 and Ɓ (Bd0→µ+µ-)\u3c3.9×10-8 at 90% confidence level
Understanding the newly observed Y(4008) by Belle
Very recently a new enhancement around 4.05 GeV was observed by Belle
experiment. In this short note, we discuss some possible assignments for this
enhancement, i.e. and molecular state. In these two
assignments, Y(4008) can decay into with comparable
branching ratio with that of . Thus one suggests
high energy experimentalists to look for Y(4008) in channel.
Furthermore one proposes further experiments to search missing channel
, and especially and
, which will be helpful to distinguish and
molecular state assignments for this new enhancement.Comment: 4 pages, 5 figures. Typos correcte
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