4,821 research outputs found
Test beam results for an upgraded forward tagger of the L3 experiment at LEP II
We have tested new scintillator modules with silicon photodiode readout for the upgraded Active Lead Rings (ALR) of the L3 detector at LEP II. Results are presented from data recorded in muon and electron test beams with particular emphasis on the light production and collection as a function of the particle impact position on the scintillator modules. The results from the beam test data will be used for the design of the readout and trigger electronics in conjunction with the required ALR performance as an electron tagger and beam background monitor at LEP II
Positronium Portal into Hidden Sector: A new Experiment to Search for Mirror Dark Matter
The understanding of the origin of dark matter has great importance for
cosmology and particle physics. Several interesting extensions of the standard
model dealing with solution of this problem motivate the concept of hidden
sectors consisting of SU(3)xSU(2)_LxU(1)_Y singlet fields. Among these models,
the mirror matter model is certainly one of the most interesting. The model
explains the origin of parity violation in weak interactions, it could also
explain the baryon asymmetry of the Universe and provide a natural ground for
the explanation of dark matter. The mirror matter could have a portal to our
world through photon-mirror photon mixing (epsilon). This mixing would lead to
orthopositronium (o-Ps) to mirror orthopositronium oscillations, the
experimental signature of which is the apparently invisible decay of o-Ps. In
this paper, we describe an experiment to search for the decay o-Ps -> invisible
in vacuum by using a pulsed slow positron beam and a massive 4pi BGO crystal
calorimeter. The developed high efficiency positron tagging system, the low
calorimeter energy threshold and high hermiticity allow the expected
sensitivity in mixing strength to be epsilon about 10^-9, which is more than
one order of magnitude below the current Big Bang Nucleosynthesis limit and in
a region of parameter space of great theoretical and phenomenological interest.
The vacuum experiment with such sensitivity is particularly timely in light of
the recent DAMA/LIBRA observations of the annual modulation signal consistent
with a mirror type dark matter interpretation.Comment: 40 pages, 29 Figures 2 Tables v2: Ref. added, Fig. 29 and some text
added to explain idea for backscattering e+ background suppression, corrected
typos v3: minor corrections: Eq 2.1 corrected (6 lines-> 5 lines), Eq.2.17:
two extra "-" signs remove
Neutralino properties in the light of a further indication of an annual modulation effect in WIMP direct search
We demonstrate that the further indication of a possible annual modulation
effect, singled out by the DAMA/NaI experiment for WIMP direct detection, is
widely compatible with an interpretation in terms of a relic neutralino as the
major component of dark matter in the Universe. We discuss the supersymmetric
features of this neutralino in the Minimal Supersymmetric extension of the
Standard Model (MSSM) and their implications for searches at accelerators.Comment: 15 pages, ReVTeX, 9 figures (included as PS files
Les Houches 2011: Physics at TeV Colliders New Physics Working Group Report
We present the activities of the "New Physics" working group for the "Physics
at TeV Colliders" workshop (Les Houches, France, 30 May-17 June, 2011). Our
report includes new agreements on formats for interfaces between computational
tools, new tool developments, important signatures for searches at the LHC,
recommendations for presentation of LHC search results, as well as additional
phenomenological studies.Comment: 243 pages, report of the Les Houches 2011 New Physics Group; fix
three figure
Observation of long-range, near-side angular correlations in pPb collisions at the LHC
This article is published Open Access at sciencedirect.com. It is distributed under the terms of the Creative Commons Attribution License 3.0.-- et al.Results on two-particle angular correlations for charged particles emitted in pPb collisions at a nucleon–nucleon center-of-mass energy of 5.02 TeV are presented. The analysis uses two million collisions collected with the CMS detector at the LHC. The correlations are studied over a broad range of pseudorapidity, η , and full azimuth, ϕ , as a function of charged particle multiplicity and particle transverse momentum, pTpT. In high-multiplicity events, a long-range (2<|Δη|<42<|Δη|<4), near-side (Δϕ≈0Δϕ≈0) structure emerges in the two-particle Δη –Δϕ correlation functions. This is the first observation of such correlations in proton–nucleus collisions, resembling the ridge-like correlations seen in high-multiplicity pp collisions at s=7 TeV and in AA collisions over a broad range of center-of-mass energies. The correlation strength exhibits a pronounced maximum in the range of pT=1–1.5 GeV/cpT=1–1.5 GeV/c and an approximately linear increase with charged particle multiplicity for high-multiplicity events. These observations are qualitatively similar to those in pp collisions when selecting the same observed particle multiplicity, while the overall strength of the correlations is significantly larger in pPb collisions.Acknowledge support from BMWF and FWF (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MEYS (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES (Croatia); RPF (Cyprus); MoER, SF0690030s09 and ERDF (Estonia); Academy of Finland, MEC, 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); MSI (New Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT (Portugal); JINR (Armenia, Belarus, Georgia, Ukraine Uzbekistan); MON, RosAtom, RAS and RFBR (Russia); MSTD (Serbia); SEIDI and CPAN (Spain); Swiss Funding Agencies (Switzerland); NSC (Taipei); ThEP, IPST and NECTEC (Thailand); TUBITAK and TAEK (Turkey); NASU (Ukraine); STFC (United Kingdom); DOE and NSF (USA).Peer Reviewe
Measurement of the Υ(1S), Υ(2S), and Υ(3S) polarizations in pp collisions at √s=7 TeV
The polarizations of the υ(1S), υ(2S), and υ(3S) mesons are measured in proton-proton collisions at √s=7 TeV, using a data sample of υ(nS)→μ+μ- decays collected by the CMS experiment, corresponding to an integrated luminosity of 4.9 fb-1. The dimuon decay angular distributions are analyzed in three different polarization frames. The polarization parameters λ™, λφ, and λ, as well as the frame-invariant quantity λ, are presented as a function of the υ(nS) transverse momentum between 10 and 50 GeV, in the rapidity ranges |y|<0.6 and 0.6<|y|<1.2. No evidence of large transverse or longitudinal polarizations is seen in the explored kinematic region. © 2013 CERN.We acknowledge support from: BMWF and FWF (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); MoER, SF0690030s09 and ERDF (Estonia); Academy of Finland, MEC, 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); MSI (New Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT (Portugal); JINR (Armenia, Belarus, Georgia, Ukraine, and Uzbekistan); MON, RosAtom, RAS, and RFBR (Russia); MSTD (Serbia); SEIDI and CPAN (Spain); Swiss Funding Agencies (Switzerland); NSC (Taipei); TUBITAK and TAEK (Turkey); STFC (United Kingdom); and DOE and NSF (USA).Peer Reviewe
Measurement of the muon decay spectrum with the ICARUS liquid Argon TPC
Examples are given which prove the ICARUS detector quality through relevant
physics measurements. We study the muon decay energy spectrum from a sample of
stopping muon events acquired during the test run of the ICARUS T600 detector.
This detector allows the spatial reconstruction of the events with fine
granularity, hence, the precise measurement of the range and dE/dx of the muon
with high sampling rate. This information is used to compute the calibration
factors needed for the full calorimetric reconstruction of the events. The
Michel rho parameter is then measured by comparison of the experimental and
Monte Carlo simulated muon decay spectra, obtaining rho = 0.72 +/- 0.06(stat.)
+/- 0.08(syst.). The energy resolution for electrons below ~50 MeV is finally
extracted from the simulated sample, obtaining (Emeas-Emc)/Emc =
11%/sqrt(E[MeV]) + 2%.Comment: 16 pages, 8 figures, LaTex, A4. Some text and 1 figure added. Final
version as accepted for publication in The European Physical Journal
Search for Branons at LEP
We search, in the context of extra-dimension scenarios, for the possible
existence of brane fluctuations, called branons. Events with a single photon or
a single Z-boson and missing energy and momentum collected with the L3 detector
in e^+ e^- collisions at centre-of-mass energies sqrt{s}=189-209$ GeV are
analysed. No excess over the Standard Model expectations is found and a lower
limit at 95% confidence level of 103 GeV is derived for the mass of branons,
for a scenario with small brane tensions. Alternatively, under the assumption
of a light branon, brane tensions below 180 GeV are excluded
Search for contact interactions using the inclusive jet pT spectrum in pp collisions at √s=7 TeV
Results are reported of a search for a deviation in the jet production cross section from the prediction of perturbative quantum chromodynamics at next-to-leading order. The search is conducted using a 7 TeV proton-proton data sample corresponding to an integrated luminosity of 5.0 fb-1, collected with the Compact Muon Solenoid detector at the Large Hadron Collider. A deviation could arise from interactions characterized by a mass scale Λ too high to be probed directly at the LHC. Such phenomena can be modeled as contact interactions. No evidence of a deviation is found. Using the CL s criterion, lower limits are set on Λ of 9.9 TeV and 14.3 TeV at 95% confidence level for models with destructive and constructive interference, respectively. Limits obtained with a Bayesian method are also reported. © 2013 CERN.Acknowledge support from BMWF and FWF (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MEYS (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES (Croatia); RPF (Cyprus); MoER, SF0690030s09 and ERDF (Estonia); Academy of Finland, MEC, 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); MSI (New Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT (Portugal); JINR (Armenia, Belarus, Georgia, Ukraine Uzbekistan); MON, RosAtom, RAS and RFBR (Russia); MSTD (Serbia); SEIDI and CPAN (Spain); Swiss Funding Agencies (Switzerland); NSC (Taipei); ThEP, IPST and NECTEC (Thailand); TUBITAK and TAEK (Turkey); NASU (Ukraine); STFC (United Kingdom); DOE and NSF (USA).Peer Reviewe
- …