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.
52995463
OBSERVATION OF TeV GAMMA RAYS FROM THE CYGNUS REGION WITH THE ARGO-YBJ EXPERIMENT
We report the observation of TeV γ-rays from the Cygnus region using the ARGO-YBJ data collected from 2007 November to 2011 August. Several TeV sources are located in this region including the two bright extended MGRO J2019+37 and MGRO J2031+41. According to the Milagro data set, at 20 TeV MGRO J2019+37 is the most significant source apart from the Crab Nebula. No signal from MGRO J2019+37 is detected by the ARGO-YBJ experiment, and the derived flux upper limits at the 90% confidence level for all the events above 600 GeV with medium energy of 3 TeV are lower than the Milagro flux, implying that the source might be variable and hard to be identified as a pulsar wind nebula. The only statistically significant (6.4 standard deviations) γ-ray signal is found from MGRO J2031+41, with a flux consistent with the measurement by Milagro.
120107147
Partial wave analysis of psi-prime ---> pi+ pi- pi0 at BESII
124881458
Updated study on multi-TeV cosmic-ray modulation with the Tibet III air shower array using the east-west method
We study the sidereal and solar time modulation of multi-TeV cosmic rays using the east-west method with Tibet III air shower array data taken from November 1999 to December 2008. The statistics are twice the amount used in our previous paper. In this analysis, the amplitude of the observed sidereal time modulation is about 0.1%, and the modulation shows an excess from about 4 to 7 hours and a deficit around 12 hours in local sidereal time. The sidereal time modulation has a weak dependence on the primary energy of the cosmic rays. However, the solar time modulation shows a large energy dependence. We find that the solar time modulation is fairly consistent with the prediction of the Compton-Getting effect for high-energy samples (6.2 TeV and 12.0 TeV), but exceeds the prediction for the low-energy sample (4.0 TeV). Such a discrepancy may be due to the solar modulation or the characteristics of the experimental device in the near threshold energy.
117145668
Attenuation study for Tibet Water Cherenkov Muon Detector Array-A
This work aims at online calibrating the signal attenuation of the long cable used in Tibet Water Cherenkov Muon detector array-A (Tibet MD-A) under the 37 000 m2 Tibet air shower array. Based on the waterproof connection of the PMT (R3600_06) with the signal cable, and the characters of the high voltage divider, terminal reflection method is explored and used for measuring the signal attenuation with a practical way to eliminate the contribution of the pulse baseline (pedestal). Comparison measurement between it and QDC (Charge-to-Digital Conversion) data taking method are carried out by using open-ended cables, confirming that terminal reflection method is a fast and convenient method, and suitable to online calibrate the signal attenuation for Tibet MD-A. At 26\degree C, the measured attenuation coefficient with the 250-m cable, permanently connected to the PMT, is ~13.9%. Also, the cable frequency response is measured by using the sinusoidal signals, which could be used to study the time dispersion of the real signal produced with Tibet MD-A detector via Fourier analysis.
123829200
Performance of the muon detector A under TIBET III array
In order to observe gamma rays in the 100 TeV energy region, the 4500 m(2) underground muon detector array using water Cherenkov technique is constructed, forming the TIBET III+MD hybrid array. Because the showers induced by primary gamma rays contain much fewer muons than those induced by primary hadrons, significant improvement of the gamma ray sensitivity for TIBET III+MD array is expected. In this paper, the design and performance of the MD-A detector with large Tyvek bag is reported.
123610392
SEARCH FOR NEW MASSIVE PARTICLES IN COSMIC RAYS
In this paper, some unusual cosmic ray events are reviewed. They are the Yunnan event recorded in 1972 using a cloud chamber at Yunnan Cosmic Ray Station (YCRS) near Kunming, the south-west of China; the six exotic events (Kolar events) collected during 1965 to 1975 in the Kolar Gold Mine Field (KGF) in south India; and a double-core event obtained also in KGF in 1979 at a depth different from that where the other six were obtained, In addition, some interesting phenomena were also noticed: the abnormal upward muon flux observed by the MINI collaboration, and several intriguing signals seen in the proton detector in KGF, A careful kinematics analysis has shown that all these exotic events are likely to be related to a kind of heavy and slow-moving (i.e. with a Lorentz factor gamma approximate to 2-5) particles produced from cosmic ray interactions. Besides, the rough flux estimates in these experiments seem to indicate that the event rate does not depend on the depth. Thus a natural hypothesis is that there is a heavy and neutral component in the cosmic rays which might be related with the long-sought weakly interacting massive particle (WIMP) - one of the most promising candidates of the dark matter of our Universe. Moreover, from the tracks seen in these events, there is also a signal of the possible existence of a kind of heavy and charged particles with a relatively long lifetime (say, longer than 10(-9) s) which might be the interacting products of the unknown cosmic ray particles mentioned above. We then turn to the question of how to search for these exotic particles in cosmic rays, and propose to build a dedicated magnetic spectrometer for identifying them.
119230663
Exact half-BPS string-junction solutions in six-dimensional supergravity
A bstractWe construct SO(2, 1) × SO(3)-invariant half-BPS solutions in six-dimensional (0,4) supergravity with m tensor multiplets. The space-time manifold of each one of these solutions consists of an AdS2 × S2 warped over a Riemann surface Σ with boundary. The most general local solution is parametrized by one real harmonic function, and m + 2 holomorphic functions which are subject to a quadratic constraint and a hermitian inequality, both of which are manifestly SO(2, m) invariant. Imposing suitable conditions on these harmonic and holomorphic functions, we construct globally regular supergravity solutions with N distinct AdS3 × S3 asymptotic regions and contractible Σ. These solutions have an intricate moduli space, whose dimension equals 2(m + 1)N − m − 2 and matches the counting of three-form charge vectors and un-attracted scalars of the tensor multiplet. Exact explicit formulas for all supergravity fields are obtained in terms of the moduli.Our solutions give the near-horizon geometries for junctions of N self-dual strings in six dimensions, and are holographic duals to CFTs defined on N half-planes which share a common interface line. For m = 5, the solutions lift to quarter-BPS solutions for sixdimensional (4,4) supergravity.
125771026
Letter of intent for the study of CP violation and heavy flavor physics at PEP-II