6,807 research outputs found
Microlensing Surveys of M31 in the Wide Field Imaging Era
The Andromeda Galaxy (M31) is the closest large galaxy to the Milky Way, thus
it is an important laboratory for studying massive dark objects in galactic
halos (MACHOs) by gravitational microlensing. Such studies strongly complement
the studies of the Milky Way halo using the the Large and Small Magellanic
Clouds. We consider the possibilities for microlensing surveys of M31 using the
next generation of wide field imaging telescopes with fields of view in the
square degree range. We consider proposals for such imagers both on the ground
and in space. For concreteness, we specialize to the SNAP proposal for a space
telescope and the LSST proposal for a ground based telescope. We find that a
modest space-based survey of 50 visits of one hour each is considerably better
than current ground based surveys covering 5 years. Crucially, systematic
effects can be considerably better controlled with a space telescope because of
both the infrared sensitivity and the angular resolution. To be competitive, 8
meter class wide-field ground based imagers must take exposures of several
hundred seconds with several day cadence.Comment: 10 pages, 4 figures, 2 table
Reconstruction and Particle Identification for a DIRC System
We study the reconstruction and particle identification (PID) problem for
Ring Imaging devices providing a good knowledge of the direction of the
Cerenkov photons, as the DIRC system, on which we specialize. We advocate first
the use of the stereographic projection as a tool allowing a suitable
representation of the photon data, as it allows to represent the Cerenkov cone
always as a circle. We set up an algorithm able to perform reliably a fit of
circle arcs of small angular opening, by minimising a true Chi2 expression. The
system we develop for PID relies on this algorithm and on a procedure able to
remove background photons with a high efficiency. We thus show that, even when
the background is large, it is possible to perform an efficient PID by means of
a fit algorithm which finally provides all the circle parameters; these are
connected with the charged track direction and its Cerenkov angle. It is shown
that background effects can be dealt without spoiling significantly the
reconstruction probability distributions.Comment: 67 pages, 23 figure
The Anomaly in the Candidate Microlensing Event PA-99-N2
The lightcurve of PA-99-N2, one of the recently announced microlensing
candidates towards M31, shows small deviations from the standard Paczynski
form. We explore a number of possible explanations, including correlations with
the seeing, the parallax effect and a binary lens. We find that the
observations are consistent with an unresolved RGB or AGB star in M31 being
microlensed by a binary lens. We find that the best fit binary lens mass ratio
is about one hundredth, which is one of most extreme values found for a binary
lens so far. If both the source and lens lie in the M31 disk, then the standard
M31 model predicts the probable mass range of the system to be 0.02-3.6 solar
masses (95 % confidence limit). In this scenario, the mass of the secondary
component is therefore likely to be below the hydrogen-burning limit. On the
other hand, if a compact halo object in M31 is lensing a disk or spheroid
source, then the total lens mass is likely to lie between 0.09-32 solar masses,
which is consistent with the primary being a stellar remnant and the secondary
a low mass star or brown dwarf. The optical depth (or alternatively the
differential rate) along the line of sight toward the event indicates that a
halo lens is more likely than a stellar lens provided that dark compact objects
comprise no less than 15 per cent (or 5 per cent) of haloes.Comment: Latex, 23 pages, 9 figures, in press at The Astrophysical Journa
57 gastrotomies sur les bovins, dans des conditions difficiles, sans complications opératoires, grùce à l'emploi systématique des antibiotiques ordinaires
First measurement of the cross section for top-quark pair production in protonâproton collisions at âs = 7 TeV
20 pĂĄginas, 3 figuras, 1 tabla.-- This article is published Open Access at sciencedirect.com. It
is distributed under the terms of the Creative Commons Attribution
License 3.0.-- CMS Collaboration: et al.The first measurement of the cross section for top-quark pair production in pp collisions at the
Large Hadron Collider at center-of-mass energy âs = 7 TeV has been performed using a data sample
corresponding to an integrated luminosity of 3.1 ± 0.3 pbâ1 recorded by the CMS detector. This result
utilizes the final state with two isolated, highly energetic charged leptons, large missing transverse
energy, and two or more jets. Backgrounds from DrellâYan and non-W/Z boson production are estimated
from data. Eleven events are observed in the data with 2.1 ± 1.0 events expected from background. The
measured cross section is 194±72(stat.)±24(syst.)±21(lumi.) pb, consistent with next-to-leading order
predictions.Acknowledge support from: FMSR (Austria);
FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP
(Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China);
COLCIENCIAS (Colombia); MSES (Croatia); RPF (Cyprus); Academy
of Sciences and NICPB (Estonia); Academy of Finland, ME, and
HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF
(Germany); GSRT (Greece); OTKA and NKTH (Hungary); DAE and
DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); NRF and WCU
(Korea); LAS (Lithuania); CINVESTAV, CONACYT, SEP, and UASLPFAI
(Mexico); PAEC (Pakistan); SCSR (Poland); FCT (Portugal); JINR
(Armenia, Belarus, Georgia, Ukraine, Uzbekistan); MST and MAE
(Russia); MSTD (Serbia); MICINN and CPAN (Spain); Swiss Funding
Agencies (Switzerland); NSC (Taipei); TUBITAK and TAEK (Turkey);
STFC (United Kingdom); DOE and NSF (USA).Peer reviewe
Search for supersymmetry in pp collisions at 7 TeV in events with jets and missing transverse energy
Acknowledge support from:
FMSR (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ,
and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC
(China); COLCIENCIAS (Colombia); MSES (Croatia); RPF (Cyprus);
Academy of Sciences and NICPB (Estonia); Academy of Finland,
ME, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG,
and HGF (Germany); GSRT (Greece); OTKA and NKTH (Hungary);
DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); NRF
and WCU (Korea); LAS (Lithuania); CINVESTAV, CONACYT, SEP, and
UASLP-FAI (Mexico); PAEC (Pakistan); SCSR (Poland); FCT (Portugal);
JINR (Armenia, Belarus, Georgia, Ukraine, Uzbekistan); MST
and MAE (Russia); MSTD (Serbia); MICINN and CPAN (Spain); Swiss
Funding Agencies (Switzerland); NSC (Taipei); TUBITAK and TAEK
(Turkey); STFC (United Kingdom); DOE and NSF (USA).A search for supersymmetry with R-parity conservation in protonâproton collisions at a centre-of-mass
energy of 7 TeV is presented. The data correspond to an integrated luminosity of 35 pbâ1 collected by
the CMS experiment at the LHC. The search is performed in events with jets and significant missing
transverse energy, characteristic of the decays of heavy, pair-produced squarks and gluinos. The primary
background, from standard model multijet production, is reduced by several orders of magnitude to a
negligible level by the application of a set of robust kinematic requirements. With this selection, the
data are consistent with the standard model backgrounds, namely tÂŻt, W + jet and Z + jet production,
which are estimated from data control samples. Limits are set on the parameters of the constrained
minimal supersymmetric extension of the standard model. These limits extend those set previously by
experiments at the Tevatron and LEP colliders.23 pĂĄginas, 5 figuras, 2 tablas.-- Open access:
This article is distributed under the terms of the Creative Commons Attribution
License 3.0.-- CMS Collaboration: et al.Peer reviewe
Measurement of WÎł and ZÎł production in pp collisions at âs = 7 TeV
21 pĂĄginas, 7 figuras, 2 tablas.-- Open access:
This article is distributed under the terms of the Creative Commons Attribution
License 3.0.-- CMS collaboration: et al.A measurement of WÎł and ZÎł production in protonâproton collisions at âs = 7 TeV is presented. Results
are based on a data sample recorded by the CMS experiment at the LHC, corresponding to an
integrated luminosity of 36 pbâ1. The electron and muon decay channels of the W and Z are used. The
total cross sections are measured for photon transverse energy EÎł
T > 10 GeV and spatial separation from
charged leptons in the plane of pseudorapidity and azimuthal angle R( ,Îł) > 0.7, and with an additional
dilepton invariant mass requirement of M > 50 GeV for the ZÎł process. The following cross
section times branching fraction values are found: Ï(ppâWÎł + X) Ă B(Wâ Îœ) = 56.3 ± 5.0(stat.) ± 5.0(syst.)±2.3(lumi.) pb and Ï(ppâZÎł + X)ĂB(Zâ ) = 9.4±1.0(stat.)±0.6(syst.)±0.4(lumi.) pb.
These measurements are in agreement with standard model predictions. The first limits on anomalous
WWÎł , ZZÎł , and Zγγ trilinear gauge couplings at âs =7 TeV are set.Acknowledge support from: FMSR (Austria);
FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP
(Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China);
COLCIENCIAS (Colombia); MSES (Croatia); RPF (Cyprus); Academy
of Sciences and NICPB (Estonia); Academy of Finland, ME, and
HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF
(Germany); GSRT (Greece); OTKA and NKTH (Hungary); DAE and
DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); NRF and WCU
(Korea); LAS (Lithuania); CINVESTAV, CONACYT, SEP, and UASLPFAI
(Mexico); PAEC (Pakistan); SCSR (Poland); FCT (Portugal); JINR
(Armenia, Belarus, Georgia, Ukraine, Uzbekistan); MST and MAE
(Russia); MSTD (Serbia); MICINN and CPAN (Spain); Swiss Funding
Agencies (Switzerland); NSC (Taipei); TUBITAK and TAEK (Turkey);
STFC (United Kingdom); DOE and NSF (USA).Peer reviewe
AGAPE, an experiment to detect MACHO's in the direction of the Andromeda galaxy
The status of the Agape experiment to detect Machos in the direction of the
andromeda galaxy is presented.Comment: 4 pages, 1 figure in a separate compressed, tarred, uuencoded uufile.
In case ofproblem contact [email protected]
Web-Appendix of: The Rich Domain of Uncertainty: Source Functions and Their Experimental Implementation.
ABSTRACT. In economic decisions we often have to deal with uncertain events for which no probabilities are known. Several normative models have been proposed for such decisions. Empirical studies have usually been qualitative, or they estimated ambiguity aversion through one single number. This paper introduces the source method, a tractable method for quantitatively analyzing uncertainty empirically that can capture the richness of ambiguity attitudes. The theoretical key in our method is the distinction between different sources of uncertainty, within which subjective (choice-based) probabilities can still be defined. Source functions convert those subjective probabilities into willingness to bet. We apply our method in an experiment, where we do not commit to particular ambiguity attitudes but let the data speak
Search for a W boson decaying to a muon and a neutrino in pp collisions at âs = 7 TeV
20 pĂĄginas, 4 figuras, 3 tablas.-- Open access:
This article is distributed under the terms of the Creative Commons Attribution
License 3.0.-- CMS Collaboration: et al.A new heavy gauge boson, W', decaying to a muon and a neutrino, is searched for in pp collisions at a
centre-of-mass energy of 7 TeV. The data, collected with the CMS detector at the LHC, correspond to an
integrated luminosity of 36 pbâ1. No significant excess of events above the standard model expectation
is found in the transverse mass distribution of the muonâneutrino system. Masses below 1.40 TeV are
excluded at the 95% confidence level for a sequential standard-model-like W'. The W' mass lower limit
increases to 1.58 TeV when the present analysis is combined with the CMS result for the electron channel.Acknowledge support from: FMSR (Austria);
FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP
(Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS
(Colombia); MSES (Croatia); RPF (Cyprus); Academy of
Sciences and NICPB (Estonia); Academy of Finland, ME, and HIP
(Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF
(Germany); GSRT (Greece); OTKA and NKTH (Hungary); DAE and
DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); NRF and WCU
(Korea); LAS (Lithuania); CINVESTAV, CONACYT, SEP, and UASLPFAI
(Mexico); PAEC (Pakistan); SCSR (Poland); FCT (Portugal); JINR
(Armenia, Belarus, Georgia, Ukraine, Uzbekistan); MST and MAE
(Russia); MSTD (Serbia); MICINN and CPAN (Spain); Swiss Funding
Agencies (Switzerland); NSC (Taipei); TUBITAK and TAEK (Turkey);
STFC (United Kingdom); DOE and NSF (USA).Peer reviewe
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