122265599
First LHC beam induced tracks reconstructed in the LHCb VELO
The Vertex Locator of the LHCb experiment has been used to fully reconstruct beam induced tracks at the LHC. A beam of protons was collided with a beam absorber during the LHC synchronisation test of the anti-clockwise beam on the weekend 22nd–24th August 2008. The resulting particles have been observed by the Vertex Locator. The LHCb Vertex Locator is a silicon micro-strip detector containing 21 planes of modules. Tracks were observed passing through up to 19 modules (38 silicon sensors). A total of over 700 tracks were reconstructed, and are being used to study the calibration and alignment of the detector.
119969840
First spatial alignment of the LHCb VELO and analysis of beam absorber collision data
A first alignment of the LHCb Vertex Locator has been obtained from beam induced tracks at the LHC. A 450 GeV/c protons were collided on a beam absorber during the LHC synchronisation tests of the anti-clockwise beam in August and September 2008. The resulting particle tracks have been reconstructed by the Vertex Locator. This was the first full reconstruction of tracks induced by the LHC beam. The quality of the data obtained is discussed. A total of 2200 tracks were reconstructed from the full data sample, and a first spatial alignment was obtained. The detector is aligned to an accuracy of Slim in the sensor plane. The results confirm that all detector modules have not been displaced from their surveyed positions by more than 10 mm. (C) 2010 Elsevier B.V. All rights reserved.
12237576
Measurement of the relative branching fraction of upsilon(4S) to charged and neutral B-meson pairs.
We analyze 9.7x10(6) B_B pairs recorded with the CLEO detector to determine the production ratio of charged to neutral B-meson pairs produced at the Upsilon(4S) resonance. We measure the rates for B0-->J/psiK((*)0) and B+-->J/psiK((*)+) decays and use the world-average B-meson lifetime ratio to extract the relative widths f(+-) / f(00) = gamma(Upsilon(4S)-->B+B-) / gamma(Upsilon(4S)-->B0 B-0)) = 1.04+/-0.07(stat)+/-0.04(syst). With the assumption that f(+-)+f(00) = 1, we obtain f(00) = 0.49+/-0.02(stat)+/-0.01(syst) and f(+-) = 0.51+/-0.02(stat)+/-0.01(syst). This production ratio and its uncertainty apply to all exclusive B-meson branching fractions measured at the Upsilon(4S) resonance.
119287240
Searches for Majorana neutrinos in $B^-$ decays
Searches for heavy Majorana neutrinos in B- decays in final states containing hadrons plus a \mu- \mu- pair have been performed using 0.41/fb of data collected with the LHCb detector in proton-proton collisions at a center-of-mass energy of 7 TeV. The D+ \mu- \mu- and D*+ \mu- \mu- final states can arise from the presence of virtual Majorana neutrinos of any mass. Other final states containing \pi+, Ds+, or D0\pi+ can be mediated by an on-shell Majorana neutrino. No signals are found and upper limits are set on Majorana neutrino production as a function of mass, and also on the B- decay branching fractions.
14029193
Performance of the CLEO III LiF-TEA ring imaging Cherenkov detector in a high-energy muon beam
Abstract The CLEO III Ring Imaging Cherenkov detector uses LiF radiators to generate Cherenkov photons which are then detected by proportional wire chambers using a mixture of CH 4 and TEA gases. The first two photon detector modules which were constructed, were taken to the Fermilab and tested in a beam dump that provided high-momentum muons. We report on results using both plane and “sawtooth”–shaped radiators. Specifically, we discuss the number of photoelectrons observed per ring and the angular resolution. The particle separation ability is shown to be sufficient for the physics of CLEO III.
42582723
Measurement of the Ds+ - Ds- production asymmetry in 7 TeV pp collisions
Article history: Received 4 May 2012 Received in revised form 30 May 2012 Accepted 1 June 2012 Available online 6 June 2012 Editor: W.-D. Schlatter Heavy quark production in 7 TeV centre-of-mass energy pp collisions at the LHC is not necessarily flavour symmetric. The production asymmetry, AP, between D+s and D−s mesons is studied using the φπ± decay mode in a data sample of 1.0 fb−1 collected with the LHCb detector. The difference between π+ and π− detection efficiencies is determined using the ratios of fully reconstructed to partially reconstructed D∗± decays. The overall production asymmetry in the D±s rapidity region 2.0 to 4.5 with transverse momentum larger than 2 GeV is measured to be AP = (−0.33 ± 0.22 ± 0.10)%. This result can constrain models of heavy flavour production. © 2012 CERN. Published by Elsevier B.V. All rights reserved.
118457510
YNOGK: A NEW PUBLIC CODE FOR CALCULATING NULL GEODESICS IN THE KERR SPACETIME
Following the work of Dexter & Agol, we present a new public code for the fast calculation of null geodesics in the Kerr spacetime. Using Weierstrass's and Jacobi's elliptic functions, we express all coordinates and affine parameters as analytical and numerical functions of a parameter p, which is an integral value along the geodesic. This is the main difference between our code and previous similar ones. The advantage of this treatment is that the information about the turning points does not need to be specified in advance by the user, and many applications such as imaging, the calculation of line profiles, and the observer-emitter problem, become root-finding problems. All elliptic integrations are computed by Carlson's elliptic integral method as in Dexter & Agol, which guarantees the fast computational speed of our code. The formulae to compute the constants of motion given by Cunningham & Bardeen have been extended, which allow one to readily handle situations in which the emitter or the observer has an arbitrary distance from, and motion state with respect to, the central compact object. The validation of the code has been extensively tested through applications to toy problems from the literature. The source FORTRAN code is freely available for download on our Web site http://www1.ynao.ac.cn/similar to yangxl/yxl.html.
56397085
Measurements of the T2K neutrino beam properties using the INGRID on-axis near detector
Precise measurement of neutrino beam direction and intensity was achieved based on a new concept with modularized neutrino detectors. INGRID (Interactive Neutrino GRID) is an on-axis near detector for the T2K long baseline neutrino oscillation experiment. INGRID consists of 16 identical modules arranged in horizontal and vertical arrays around the beam center. The module has a sandwich structure of iron target plates and scintillator trackers. INGRID directly monitors the muon neutrino beam profile center and intensity using the number of observed neutrino events in each module. The neutrino beam direction is measured with accuracy better than 0.4 mrad from the measured profile center. The normalized event rate is measured with 4% precision.
9792067
A Comprehensive Study of 2000 Narrow Line Seyfert 1 Galaxies from the Sloan Digital Sky Survey. I. The Sample
This is the first paper in a series dedicated to the study of the emission-line and continuum properties of narrow line Seyfert 1 galaxies (NLS1s). We carried out a systematic search for NLS1s from objects assigned as "QSOs'' or "galaxies'' in the spectroscopic sample of the Sloan Digital Sky Survey Data Release 3 (SDSS DR3) by a careful modeling of their emission lines and continua. The result is a uniform sample comprising similar to 2000 NLS1s. This sample dramatically increases the number of known NLS1s by a factor of similar to 10 over previous compilations. This paper presents the parameters of the prominent emission lines and continua, which were measured accurately with typical uncertainties < 10%. Taking advantage of such an unprecedented large and uniform sample with accurately measured spectral parameters, we carried out various statistical analyses, some of which were only possible for the first time. The main results found are as follows. (1) Within the overall Seyfert 1 population, the incidence of NLS1s is strongly dependent on the optical, X-ray, and radio luminosities as well as the radio loudness. The fraction of NLS1s peaks around SDSS g-band absolute magnitude M-g similar to -22 mag in the optical and similar to 10(43.2) ergs s(-1) in the soft X-ray band, and decreases quickly as the radio loudness increases. (2) On average the relative Fe II emission, R-4570 = Fe II lambda lambda 4434-4684/H beta, in NLS1s is about twice that in normal active galactic nuclei (AGNs) and is anticorrelated with the broad component width of the Balmer emission lines. (3) The well-known anticorrelation between the width of broad low-ionization lines and the soft X-ray spectral slope for broad line AGNs extends down to FWHM similar to 1000 km s(-1) in NLS1s, but the trend appears to reverse at still smaller line widths. (4) The equivalent width of H beta and Fe II emission lines are strongly correlated with the H beta and continuum luminosities. (5) We do not find any difference between NLS1s and normal AGNs in regard to the narrow line region. (6) We have examined the black hole mass versus stellar velocity dispersion (M-BH-sigma(*)) relation for a subsample of 308 NLS1s for which sigma(*) could be measured directly from fitting the starlight in the SDSS spectra with our stellar spectral templates. A significant correlation between M-BH and sigma(*) is found, but with the bulk of black hole masses falling below the values expected from the M-BH-sigma(*) relation for normal galaxies and normal AGNs. This result indicates that NLS1s are underage AGNs, where the growth of the SMBH lags behind the formation of the galactic bulge. (7) We also find that the FWHM of [N II] line is well correlated with sigma(*) in 206 NLS1s, for which both parameters could be derived with reasonable accuracy. The [N II] width can predict the stellar velocity dispersion to an accuracy of similar to 30%. A similar M-BH-sigma(*) relation could be found for a larger sample of 613 NLS1s on making use of the more reliable measurements of FWHM[N II].
23658132
First look at the beam test results of the FPIX2 readout chip for the BTeV silicon pixel detector
High energy and nuclear physics experiments need tracking devices with increasing spatial precision and readout speed in the face of ever-higher track densities and increased radiation environments. The new generation of hybrid pixel detectors (arrays of silicon diodes bump bonded to arrays of front-end electronic cells) is the technology able to meet these challenges. We report the first results of the BTeV silicon pixel detector beam test carried out at Fermilab in summer 2004. Tests were performed using a 120 GeV/c proton beam incident on a 6 plane pixel detector telescope. The last prototype developed for the BTeV experiment (FPIX2) is tested in the middle of the telescope. There is no external trigger, and events were built using the time-stamp information provided by the readout chips
123343846
Direct evidence for neutrino flavor transformation from neutral-current interactions in SNO
The Sudbury Neutrino Observatory (SNO) is a 1,000 tonne heavy water Cerenkov‐based neutrino detector situated 2,000 meters underground in INCO’s Creighton Mine near Sudbury, Ontario, Canada. For the neutrinos from 8B decay in the Sun SNO observes the Charged Current neutrino reaction sensitive only to electron neutrinos and others (Neutral Current and Elastic Scattering) sensitive to all active neutrino types and thereby can search for direct evidence of neutrino flavor change. Using these reactions and assuming the standard 8B shape, the ve component of the 8B solar flux is φe = 1.76−0.05+0.05(stat.)−0.09+0.09 (syst.) × 106 cm−2s−1 for a kinetic energy threshold of 5 MeV. The non‐ve component is φμτ = 3.41−0.45+0.45(stat.)−0.45+0.48 (syst.) × 106 cm−2s−1, 5.3σ greater than zero, providing strong evidence for solar ve flavor transformation. The total flux measured with the NC reaction is φNC = 5.09−0.43+0.44(stat.)−0.43+0.46 (syst.) × 106 cm−2s−1, consistent with solar models. For charged current events, ...