123410881
Test of the hadronic interaction models at around *10 TeV with Tibet EAS core data
A hybrid experiment has been started by ASγ collaboration at Tibet, China, since May 2009, that consists of a burst-detector-grid (YAC, Yangbajing Air shower Core array) and the Tibet air-shower array (Tibet-III). The first step of YAC, called YAC-I, contains 16 detector units and observes high energy electromagnetic particles in air-shower cores within several meters from the shower axis, and Tibet-III array measures the total energy and the arrival direction of air showers. YAC-I is used to check hadronic interaction models currently used for air-shower simulations such as QGSJET, SIBYLL , EPOS etc. through the multi-parameter measurement in air-shower cores. In this paper, we used a data set collected from May 1st 2009 through February 23rd 2010 by the YAC-I. The effective live time used for the present analysis is 169.65 days. The preliminary results of the interaction model checking at *10 TeV energy region is reported in this paper.
125260045
Evidence of sigma particle in J / psi ---> omega pi pi
119348940
Detecting the dark matter annihilation at the ground EAS detectors
Abstract In this paper we study the possibility of detecting gamma rays from dark matter annihilation in the subhalos of the Milky Way by the ground based EAS detectors within the frame of the minimal supersymmetric Standard Model. Based on the Monte Carlo simulation we also study the properties of two specific EAS detectors, the ARGO and HAWC, and the sensitivities of these detectors on the detection of dark matter annihilation. We find the ground EAS detectors have the possibility to observe such signals. Conversely if no signal observed we give the constraints on the supersymmetric parameter space, which however depends on the subhalos properties.
209869998
Observation of the decay psi(2S) ---> K*(892)anti-K + c.c.
124457067
Search for Invisible Decays of eta and eta-prime in the Processes J/psi ---> phi eta and phi eta-prime
Using a data sample of 58x10{sup 6} J/{psi} decays collected with the Beijing Spectrometer II detector at the Beijing Electron Positron Collider, searches for invisible decays of {eta} and {eta}{sup '} in J/{psi} to {phi}{eta} and {phi}{eta}{sup '} are performed. The {phi} signals, which are reconstructed in K{sup +}K{sup -} final states, are used to tag the {eta} and {eta}{sup '} decays. No signals are found for the invisible decays of either {eta} or {eta}{sup '}, and upper limits at the 90% confidence level are determined to be 1.65x10{sup -3} for the ratio (B({eta}{yields}invisible)/B({eta}{yields}{gamma}{gamma})) and 6.69x10{sup -2} for (B({eta}{sup '}{yields}invisible)/B({eta}{sup '}{yields}{gamma}{gamma})). These are the first searches for {eta} and {eta}{sup '} decays into invisible final states.
54761229
Energy spectrum of cosmic protons and helium nuclei by a hybrid measurement at 4300 m a.s.l.
The energy spectrum of cosmic Hydrogen and Helium nuclei has been measured below the so-called "knee" by using a hybrid experiment with a wide field-of-view Cherenkov telescope and the Resistive Plate Chamber (RPC) array of the ARGO-YBJ experiment at 4300 m above sea level. The Hydrogen and Helium nuclei have been well separated from other cosmic ray components by using a multi-parameter technique. A highly uniform energy resolution of about 25% is achieved throughout the whole energy range (100–700 TeV). The observed energy spectrum is compatible with a single power law with index γ=−2.63±0.06.
120264451
A search for flaring very-high-energy cosmic gamma-ray sources with the L3+C muon spectrometer
The L3+C muon detector at the CERN electron-positron collider, LEP, is used for the detection of very-high-energy cosmic gamma-ray sources through the observation of muons of energies above 20, 30, 50 and 100 GeV. Daily or monthly excesses in the rate of single-muon events pointing to some particular direction in the sky are searched for. The periods from mid July to November 1999, and April to November 2000 are considered. Special attention is also given to a selection of known gamma-ray sources. No statistically significant excess is observed for any direction or any particular source. (c) 2006 Elsevier B.V. All rights reserved.
122329451
TPC90, a test model for the ALEPH time projection chamber☆
Abstract A test model has been built to study the performance of prototypes for the ALEPH Time Projection Chamber. The device consists of a solenoid magnet providing a magnetic field up to 1.2 T inside a cylindric field cage of 75 cm diameter and 1.3 m length. It has been used to test two chambers of different design. We describe the setup and present results from measurements with these prototype chambers using laser beams and cosmic ray particles.
122638974
Centrality dependence of dihadron correlations and azimuthal anisotropy harmonics in PbPb collisions at $\sqrt{s_{NN}}= 2.76\ \mbox{TeV}$
Measurements from the CMS experiment at the LHC of dihadron correlations for charged particles produced in PbPb collisions at a nucleon–nucleon centre-of-mass energy of 2.76 TeV are presented. The results are reported as a function of the particle transverse momenta (pT) and collision centrality over a broad range in relative pseudorapidity (Δη) and the full range of relative azimuthal angle (Δϕ). The observed two-dimensional correlation structure in Δη and Δϕ is characterised by a narrow peak at (Δη,Δϕ)≈(0,0) from jet-like correlations and a long-range structure that persists up to at least |Δη|=4. An enhancement of the magnitude of the short-range jet peak is observed with increasing centrality, especially for particles of pT around 1–2 GeV/c. The long-range azimuthal dihadron correlations are extensively studied using a Fourier decomposition analysis. The extracted Fourier coefficients are found to factorise into a product of single-particle azimuthal anisotropies up to pT≈3–3.5 GeV/c for at least one particle from each pair, except for the second-order harmonics in the most central PbPb events. Various orders of the single-particle azimuthal anisotropy harmonics are extracted for associated particle pT of 1–3 GeV/c, as a function of the trigger particle pT up to 20 GeV/c and over the full centrality range.
118734439
Search for exotic resonances decaying into WZ/ZZ in pp collisions at $ \sqrt{s}=7 $ TeV
A bstractA search for new exotic particles decaying to the VZ final state is performed, where V is either a W or a Z boson decaying into two overlapping jets and the Z decays into a pair of electrons, muons or neutrinos. The analysis uses a data sample of pp collisions corresponding to an integrated luminosity of 5 fb−1 collected by the CMS experiment at the LHC at $ \sqrt{s}=7 $ TeV in 2011. No significant excess is observed in the mass distribution of the VZ candidates compared with the background expectation from standard model processes. Model-dependent upper limits at the 95% confidence level are set on the product of the cross section times the branching fraction of hypothetical particles decaying to the VZ final state as a function of mass. Sequential standard model W′ bosons with masses between 700 and 940 GeV are excluded. In the Randall-Sundrum model for graviton resonances with a coupling parameter of 0.05, masses between 750 and 880 GeV are also excluded.
122601384
Studies of wire gain and track distortion near the sector edges of the ALEPH time projection chamber
Abstract The materials used to hold the wires at the sector edges in a large Time Projection Chamber (TPC) inrtoduce distortions of the electric drift field near those edges. These distortions degrade tracking information and sometimes cause large changes in wire gain near the edge. We have studied these two problems for the ALEPH TPC and have found that both can be greatly reduced by the addition of two field correction strips held at appropriate voltages.