54198577
Freeze-out radii extracted from three-pion cumulants in pp, p-Pb and Pb-Pb collisions at the LHC
In high-energy collisions, the spatio-temporal size of the particle production region can be measured using the Bose-Einstein correlations of identical bosons at low relative momentum. The source radii are typically extracted using two-pion correlations, and characterize the system at the last stage of interaction, called kinetic freeze-out. In low-multiplicity collisions, unlike in high-multiplicity collisions, two-pion correlations are substantially altered by background correlations, e. g. mini-jets. Such correlations can be suppressed using three-pion cumulant correlations. We present the first measurements of the size of the system at freeze-out extracted from three-pion cumulant correlations in pp, p-Pb and Pb-Pb collisions at the LHC with ALICE. At similar multiplicity, the invariant radii extracted in p-Pb collisions are found to be 5-15% larger than those in pp, while those in Pb-Pb are 35-55% larger than those in p-Pb. Our measurements disfavor models which incorporate substantially stronger collective expansion in p-Pb as compared to pp collisions at similar multiplicity. (C) 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license
13085576
Alignment of the ALICE inner tracking system with cosmic-ray tracks
ALICE (A Large Ion Collider Experiment) is the LHC (Large Hadron Collider) experiment devoted to investigating the strongly interacting matter created in nucleus-nucleus collisions at the LHC energies. The ALICE ITS, Inner Tracking System, consists of six cylindrical layers of silicon detectors with three different technologies; in the outward direction: two layers of pixel detectors, two layers each of drift, and strip detectors. The number of parameters to be determined in the spatial alignment of the 2198 sensor modules of the ITS is about 13,000. The target alignment precision is well below 10 mu m in some cases (pixels). The sources of alignment information include survey measurements, and the reconstructed tracks from cosmic rays and from proton-proton collisions. The main track-based alignment method uses the Millepede global approach. An iterative local method was developed and used as well. We present the results obtained for the ITS alignment using about 10(5) charged tracks from cosmic rays that have been collected during summer 2008, with the ALICE solenoidal magnet switched off.
7670434
Transverse momentum spectra of charged particles in proton-proton collisions at sqrt(s) = 900 GeV with ALICE at the LHC
The inclusive charged particle transverse momentum distribution is measured in proton-proton collisions at $\sqrt{s} = 900$~GeV at the LHC using the ALICE detector. The measurement is performed in the central pseudorapidity region $(|\eta|_{\rm INEL}=0.483\pm0.001$~(stat.)~$\pm0.007$~(syst.)~GeV/$c$ and $\left_{\rm NSD}=0.489\pm0.001$~(stat.)~$\pm0.007$~(syst.)~GeV/$c$, respectively. The data exhibit a slightly larger $\left$ than measurements in wider pseudorapidity intervals. The results are compared to simulations with the Monte Carlo event generators PYTHIA and PHOJET
118591758
Longitudinal phase‐space measurements at IUCF
Synchrotron motion in the IUCF cooler ring was studied using turn‐by‐turn beam tracking on ten‐turn intervals, where the beam phase relative to the rf and the closed‐orbit position in a high‐dispersion region were measured. The synchrotron tune shift with amplitude was measured and is compared with theory. The driven response of the system was also studied using the same techniques, and was found to share many of the same characteristics of other parametric resonant systems. The experimental results did not exhibit any effects of bunch decoherence expected from the tune shift with amplitude.
119216112
Neutron spectroscopic factors of 7Li and astrophysical 6Li(n,g)7Li reaction rates
Angular distributions of the 7Li(6Li, 6Li)7Li elastic scattering and the 7Li(6Li, 7Lig.s.)6Li, 7Li(6Li, 7Li0.48)6Li transfer reactions at Ec.m. = 23.7 MeV are measured with the Q3D magnetic spectrograph. The optical potential of 6Li + 7Li is obtained by fitting the elastic scattering differential cross sections. Based on the distorted wave Born approximation (DWBA) analysis, spectroscopic factors of 7Li = 6Li ⊗ n are determined to be 0.73 ± 0.05 and 0.90 ± 0.09 for the ground and first exited states in 7Li, respectively. Using the spectroscopic factors, the cross sections of the 6Li(n, γ0, 1)7Li direct neutron capture reactions and the astrophysical 6Li(n, γ)7Li reaction rates are derived.
118389996
Neutron–gamma discrimination of CsI(Na) crystals for dark matter searches
Abstract The luminescent properties of CsI(Na) crystals are studied in this report. Using a TDS3054C oscilloscope with a sampling frequency of 5 GS/s, we find out that nuclear recoil signals are dominated by a very fast light pulse with a decay time of ∼20 ns, while γ-ray signals have a decay time of ∼600 ns. The study of n / γ separation shows that the rejection factor can reach an order of 10 −7 with a signal efficiency of more than 80% at an equivalent electron recoil energy of 20 keV or more, and the quality factors are ∼10 times smaller than that for CsI(Tl) crystals in the corresponding energy region. It is suggested that the wavelength of nuclear recoil and γ-ray signals is also different. Such a property makes CsI(Na) an ideal candidate for dark matter searches.
118367621
Measurement of the tau lifetime
With use of three-prong tau decays observed by the Mark II detector at the Stanford Linear Accelerator Center (PEP), the tau lifetime is measured to be (4.6 +- 1.9) x 10/sup -13/ sec.
122736493
Cosmic-ray energy spectrum around the knee obtained by the Tibet experiment and future prospects
The observation of the extensive air showers has been carried out since 1990 by Tibet air-shower array to study the origin of the cosmic-rays. In order to investigate the chemical composition around the knee, air-shower core detector was used in two experimental phases aiming to separate light primary elements (proton and helium). In a first phase experiment made in 1996-1999, primary proton and helium spectra were measured using a hybrid detector consisted of Tibet II air-shower array, emulsion chambers, and burst detectors. The result indicated that the fraction of light elements among the all particle spectrum is less than 30%. We performed the second phase experiment in 2002-2005 to measure proton + helium together to confirm the previous result with higher statistics by improving the detection efficiency for the air-shower cores. The P + He spectrum was obtained in a good agreement with previous result by several times higher statistics. The flux of the light elements, together with the all-particle energy spectrum, indicates the dominance of nuclei heavier than helium in the energy range around the knee. We also present the outline of the next phase experiment, which is to measure the heavy elements around the knee, using low threshold air-shower core detector named YAC. (C) 2010 COSPAR. Published by Elsevier Ltd. All rights reserved.