121851251
The forward muon detector of L3
The forward-backward muon detector of the L3 experiment is presented. Intended to be used for LEP 200 physics, it consists of 96 self-calibrating drift chambers of a new design enclosing the magnet pole pieces of the L3 solenoid. The pole pieces are toroidally magnetized to form two independent analyzing spectrometers. A novel trigger is provided by resistive plate counters attached to the drift chambers. Details about the design, construction and performance of the whole system are given together with results obtained during the 1995 running at LEP.
122717574
Search for neutralinos in Z decays
Abstract We have searched for neutralinos produced via the reactions e + e − → χχ′ and e + e − → χ′χ′, where the next-to lightest neutralino, χ′, decays into the lightest neutralino, χ, and either a photon or a fermion pair. Based on 1.8 × 10 6 hadronic Z decays collected with the L3 detector at LEP, no signal has been observed. We present upper limits of a few times 10 −5 on the branching ratios Z → χχ′ and Z → χ′χ′. In the framework of the Minimial Supersymmetric Standard Model, we exclude a lightest χ with m χ less than 18 GeV, if either tan β > 2 or the gluino mass m ≈ g > 100 GeV.
96104178
Development and operation of gas catchers to thermalize fusion–evaporation and fragmentation products
Abstract A new approach to the production of low energy radioactive beams involves the stopping of fast beams produced by fragmentation, in-flight fission or fusion–evaporation reaction into a large gas catcher where the reaction products are thermalized in high-purity helium and extracted as singly charged ions for post-acceleration. This removes the limitation present in standard ISOL technique for species that are difficult to extract from the target/ion source assembly. This approach has been implemented at Argonne since 1998 to inject fusion–evaporation products in an ion trap system. Via a series of improvements since then, we now reach efficiencies for these devices of close to 50% with delay times below 10 ms. In preparation for the RIA project, a larger device for stopping fragmentation products is in preparation. The basic principles behind these devices together with results obtained and experience gained operating these devices will be presented. Preparation for a test of the large gas cell at the full RIA energy at GSI will also be presented.
122751074
Production of single W bosons at LEP
We report on the observation of single W boson production in a data sample collected by the L3 detector at LEP2. The signal consists of large missing energy final states with a single energetic lepton or two hadronic jets. The cross-section is measured to be 0.61(-0.33)(+0.43) +/- 0.05 pb at the centre of mass energy root s = 172 GeV, consistent with the Standard Model expectation. From this measurement the following limits on the anomalous gamma WW gauge couplings are derived at 95% CL: -3.6 < Delta kappa gamma < 1.5 and -3.6 < lambda gamma < 3.6. (C) 1997 Published by Elsevier Science B.V.
14588649
Production of e, mu and tau pairs in untagged two-photon collisions at LEP
The two-photon collision reaction e+e- --> e+e-l+l- has been studied at root(s) ~ 91 GeV using the L3 detector at LEP for l = e, muon , tau. We have analysed untagged configurations where the two photons are quasi-real. Good agreement is found between our measurements and the order alpha**4 QED expectation.
11916638
Precise mass measurement of 68Se, a waiting-point nuclide along the rp process.
Mass measurements of 68Ge, 68As, and 68Se have been obtained with the Canadian Penning Trap mass spectrometer. The results determine the mass excess of 68Se as -54 232(19) keV, the first measurement with a precision and reliability sufficient to address the light-curve and energy output of x-ray bursts as well as the abundances of the elements synthesized. Under typical conditions used for modeling x-ray bursts, 68Se is found to cause a significant delay in the rp process nucleosynthesis.
119201656
VARIABILITY IN THE ORBITAL PROFILES OF THE X-RAY EMISSION OF THE γ-RAY BINARY LS I +61° 303
We report on the analysis of Rossi X-Ray Timing Explorer Proportional Counter Array (PCA) monitoring observations of the γ-ray binary system LS I +61° 303, covering 35 full cycles of its orbital motion. This constitutes the largest continuous X-ray-monitoring data set analyzed to date for this source. Such an extended analysis allows us to report (1) the discovery of variability in the orbital profiles of the X-ray emission, (2) the existence of a few (recent) short flares on top of the overall behavior typical of the source, which, given the PCA field of view, may or may not be associated with LS I +61° 303, and (3) the determination of the orbital periodicity using soft X-ray data alone.
121992643
The Wigner Functions for a Spin-1/2 Relativistic Particle in the Presence of Magnetic Field
This paper provides a study of Wigner functions for a spin-1/2 relativistic particle in the presence of magnetic field. Since the Dirac equation is described as a matrix equation, it is necessary to describe the Wigner function as a matrix function in phase space. What’s more, this function is then proved to satisfy the Dirac equation with ⋆-product. Finally, by solving the ⋆-product Dirac equation, the energy levels as well as the Wigner functions for a spin-1/2 relativistic particle in the presence of magnetic field are obtained.
118924562
The leptophilic dark matter with $Z'$ interaction: from indirect searches to future $e^+ e^-$ collider searches
We investigate the scenario where the dark matter only interacts with the charged leptons in the standard model via a neutral vector mediator $Z'$. Such a scenario with a 430 GeV dark matter can fit the recent positron fluxes observed by the AMS-02 Collaborations, with the reasonable boost factors. We study the possibility of searching such leptophilic $Z'$ via its lepton final states and invisible decay modes at the future electron-positron colliders, such as the International Linear Collider (ILC) and the Compact Linear Collider (CLIC). We find that for the benchmark models with $Z'$ mass from 1.0 TeV to 1.5 TeV, the searches for the invisible decays of $Z'\to \bar \chi \chi$ is easily achieved at the CLIC 1.5 TeV runs via the mono-photon process. However, lighter $Z'$ with mass from 0.5 TeV to 0.8 TeV are challenging to see. The di-lepton plus single photon channel can reveal the $Z'$ mass at the ILC and CLIC with moderate luminosities.
43343529
Beam instabilities measurement and cures at HLS
In Hefei light source (HLS), coupled-bunch instabilities are major limiting factors in achieving higher beam intensity while maintaining good beam quality. To Measure and suppress beam instabilities, turn-by-turn (TBT) measurement and bunch-by-bunch(BxB) measurement & feedback system are under commission [1][2]. The design of the two systems and primary experiment results is presented. Measurement and detail analysing results in injection status will also be shown.
121992013
DESCRIPTION OF THE BTEV DETECTOR
BTeV is an experiment being constructed at the Fermilab collider, designed to study mixing, CP violation, and rare decays of beauty and charm hadrons. The detector covers the forward region (10-300 mrad), components include silicon pixels, tracking, RICH, PdWO4 electromagnetic calorimeter, and muon system. Brief description of individual detector elements are presented.