1,954 research outputs found
ATLAS Monitored Drift Tube Chambers in E = 11 MeV Neutron Background
The influence of fast neutrons on the occupancy and the single tube
resolution of ATLAS muon drift detectors was investigated by exposing a chamber
built out of 3 layers of 3 short standard drift tubes to neutron flux-densities
of up to 16 kHz/cm2 at a neutron energy of E=11 MeV. Pulse shape capable NE213
scintillaton detectors and a calibrated BF3 neutron detector provided
monitoring of the neutron flux-density and energy. The sensitivity of the drift
chamber to the neutrons was measured to be 4*10-4 by comparing data sets with
and without neutron background. For the investigation of tracks of cosmic muons
two silicon-strip detectors above and underneath the chamber allow to compare
measured drift-radii with reference tracks. Alternatively, the single tube
resolution was determined using the triple-sum method. The comparison between
data with and without neutron irradiation shows only a marginal effect on the
resolution and little influence on the muon track reconstruction.Comment: 4 pages, 11 figures, conferenc
A Cosmic Ray Measurement Facility for ATLAS Muon Chambers
Monitored Drift Tube (MDT) chambers will constitute the large majority of
precision detectors in the Muon Spectrometer of the ATLAS experiment at the
Large Hadron Collider at CERN. For commissioning and calibration of MDT
chambers, a Cosmic Ray Measurement Facility is in operation at Munich
University. The objectives of this facility are to test the chambers and
on-chamber electronics, to map the positions of the anode wires within the
chambers with the precision needed for standalone muon momentum measurement in
ATLAS, and to gain experience in the operation of the chambers and on-line
calibration procedures.
Until the start of muon chamber installation in ATLAS, 88 chambers built at
the Max Planck Institute for Physics in Munich have to be commissioned and
calibrated. With a data taking period of one day individual wire positions can
be measured with an accuracy of 8.3 micrometers in the chamber plane and 27
micrometers in the direction perpendicular to that plane.Comment: 14+1 pages, 11 figures, contributed paper to the EPS2003 conference,
Aache
The Fourth Standard Model Family and the Competition in Standart Model Higgs Boson Search at Tevatron and LHC
The impact of the fourth Standard Model family on Higgs boson search at
Tevatron and LHC is reviewed.Comment: 7 pages, 13 figure
Evidence for Z(c)(+/-)(3900) in semi-inclusive decays of b-flavored hadrons
We present evidence for the exotic charged charmoniumlike state Z(c)(+/-)(3900) decaying to J/psi pi(+/-) in semi-inclusive weak decays of b-flavored hadrons. The signal is correlated with a parent J/psi pi(+)pi(-) system in the invariant-mass range 4.2-4.7 GeV that would include the exotic structure Y(4260). The study is based on 10.4 fb(-1) of p (p) over bar collision data collected by the D0 experiment at the Fermilab Tevatron collider
Dirac Neutrino Dark Matter
We investigate the possibility that dark matter is made of heavy Dirac
neutrinos with mass in the range [O(1) GeV- a few TeV] and with suppressed but
non-zero coupling to the Standard Model Z as well as a coupling to an
additional Z' gauge boson. The first part of this paper provides a
model-independent analysis for the relic density and direct detection in terms
of four main parameters: the mass, the couplings to the Z, to the Z' and to the
Higgs. These WIMP candidates arise naturally as Kaluza-Klein states in
extra-dimensional models with extended electroweak gauge group SU(2)_L* SU(2)_R
* U(1). They can be stable because of Kaluza-Klein parity or of other discrete
symmetries related to baryon number for instance, or even, in the low mass and
low coupling limits, just because of a phase-space-suppressed decay width. An
interesting aspect of warped models is that the extra Z' typically couples only
to the third generation, thus avoiding the usual experimental constraints. In
the second part of the paper, we illustrate the situation in details in a
warped GUT model.Comment: 35 pages, 25 figures; v2: JCAP version; presentation and plots
improved, results unchange
Cosmic ray tests of the D0 preshower detector
The D0 preshower detector consists of scintillator strips with embedded
wavelength-shifting fibers, and a readout using Visible Light Photon Counters.
The response to minimum ionizing particles has been tested with cosmic ray
muons. We report results on the gain calibration and light-yield distributions.
The spatial resolution is investigated taking into account the light sharing
between strips, the effects of multiple scattering and various systematic
uncertainties. The detection efficiency and noise contamination are also
investigated.Comment: 27 pages, 24 figures, submitted to NIM
Search for Kaluza-Klein Graviton Emission in Collisions at TeV using the Missing Energy Signature
We report on a search for direct Kaluza-Klein graviton production in a data
sample of 84 of \ppb collisions at = 1.8 TeV, recorded
by the Collider Detector at Fermilab. We investigate the final state of large
missing transverse energy and one or two high energy jets. We compare the data
with the predictions from a -dimensional Kaluza-Klein scenario in which
gravity becomes strong at the TeV scale. At 95% confidence level (C.L.) for
=2, 4, and 6 we exclude an effective Planck scale below 1.0, 0.77, and 0.71
TeV, respectively.Comment: Submitted to PRL, 7 pages 4 figures/Revision includes 5 figure
Measurement of the average time-integrated mixing probability of b-flavored hadrons produced at the Tevatron
We have measured the number of like-sign (LS) and opposite-sign (OS) lepton
pairs arising from double semileptonic decays of and -hadrons,
pair-produced at the Fermilab Tevatron collider. The data samples were
collected with the Collider Detector at Fermilab (CDF) during the 1992-1995
collider run by triggering on the existence of and candidates
in an event. The observed ratio of LS to OS dileptons leads to a measurement of
the average time-integrated mixing probability of all produced -flavored
hadrons which decay weakly, (stat.)
(syst.), that is significantly larger than the world average .Comment: 47 pages, 10 figures, 15 tables Submitted to Phys. Rev.
Deep-Inelastic Inclusive ep Scattering at Low x and a Determination of alpha_s
A precise measurement of the inclusive deep-inelastic e^+p scattering cross
section is reported in the kinematic range 1.5<= Q^2 <=150 GeV^2 and
3*10^(-5)<= x <=0.2. The data were recorded with the H1 detector at HERA in
1996 and 1997, and correspond to an integrated luminosity of 20 pb^(-1). The
double differential cross section, from which the proton structure function
F_2(x,Q^2) and the longitudinal structure function F_L(x,Q^2) are extracted, is
measured with typically 1% statistical and 3% systematic uncertainties. The
measured partial derivative (dF_2(x,Q^2)/dln Q^2)_x is observed to rise
continuously towards small x for fixed Q^2. The cross section data are combined
with published H1 measurements at high Q^2 for a next-to-leading order DGLAP
QCD analysis.The H1 data determine the gluon momentum distribution in the range
3*10^(-4)<= x <=0.1 to within an experimental accuracy of about 3% for Q^2 =20
GeV^2. A fit of the H1 measurements and the mu p data of the BCDMS
collaboration allows the strong coupling constant alpha_s and the gluon
distribution to be simultaneously determined. A value of alpha
_s(M_Z^2)=0.1150+-0.0017 (exp) +0.0009-0.0005 (model) is obtained in NLO, with
an additional theoretical uncertainty of about +-0.005, mainly due to the
uncertainty of the renormalisation scale.Comment: 68 pages, 24 figures and 18 table
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