We present a measurement of top quark polarization in t (t) over bar pair production in p (p) over bar collisions at root s = 1.96 TeV using data corresponding to 9.7 fb(-1) of integrated luminosity ...recorded with the D0 detector at the Fermilab Tevatron Collider. We consider final states containing a lepton and at least three jets. The polarization is measured through the distribution of lepton angles along three axes: the beam axis, the helicity axis, and the transverse axis normal to the t (t) over bar production plane. This is the first measurement of top quark polarization at the Tevatron using lepton + jet final states and the first measurement of the transverse polarization in t (t) over bar production. The observed distributions are consistent with standard model predictions of nearly no polarization.
We present a measurement of the correlation between the spins of t and (t) over bar quarks produced in proton-antiproton collisions at the Tevatron Collider at a center-of-mass energy of 1.96 TeV. We ...apply a matrix element technique to dilepton and single-lepton+jets final states in data accumulated with the DO detector that correspond to an integrated luminosity of 9.7 fb(-1). The measured value of the correlation coefficient in the off-diagonal basis, O-off = 0.89 +/- 0.22 (stat + syst), is in agreement with the standard model prediction, and represents evidence for a top-antitop quark spin correlation difference from zero at a level of 4.2 standard deviations.
Prolonged and severe sleep deprivation is associated with alterations of natural and cellular immune function. To determine whether alterations of immune function also occur after even a modest loss ...of sleep, the effects of early-night partial sleep deprivation on circulating numbers of white blood cells, natural killer (NK) cell number and cytotoxicity, lymphokine-activated killer (LAK) cell number and activity, and stimulated interleukin-2 (IL-2) production were studied in 42 medically and psychiatrically healthy male volunteers. After a night of sleep deprivation between 10 P.M. and 3 A.M., a reduction of natural immune responses as measured by NK cell activity, NK activity per number of NK cells, LAK activity, and LAK activity per number of LAK precursors (CD16,56, CD25) was found. In addition, concanavalin A-stimulated IL-2 production was suppressed after sleep deprivation due to changes in both adherent and nonadherent cell populations. After a night of recovery sleep, NK activity returned to baseline levels and IL-2 production remained suppressed. These data implicate sleep in the modulation of immunity and demonstrate that even a modest disturbance of sleep produces a reduction of natural immune responses and T cell cytokine production.
Jet energy scale determination in the DO experiment Augsten, K.; Avila, C.; Bandurin, D. V. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2014, Letnik:
763
Journal Article
Recenzirano
Odprti dostop
The calibration of jet energy measured in the DO detector is presented, based on p (p) over bar collisions at a center-of-mass energy of 1.96 TeV at the Fermilab Tevatron collider, jet energies are ...measured using a sampling calorimeter composed of uranium and liquid argon as the passive and active media, respectively. This paper describes the energy calibration of jets performed with gamma+jet, Z+jet and dilet events, with jet transverse momentum p(T) > 6 GeV and pseudorapidity range vertical bar eta vertical bar < 3.6, The corrections are measured separately for data and simulation, achieving a precision of 1.4-1.8% for jets in the central part of the calorimeter ancl up to 3.5% for the jets with pseudorapidity vertical bar eta vertical bar = 3.0. Specific corrections are extracted to enhance the description of jet energy in simulation and in particular of the effects due to the flavor of the parton originating the jet, correcting biases up to 3-4% in jets with low PT originating from gluons and up to 6-8% in jets from b quarks. Published by Elsevier B.V.
The Level-2 muon trigger at D0 Fortner, M.; Maciel, A.; Evans, H. ...
IEEE transactions on nuclear science,
08/2002, Letnik:
49, Številka:
4
Journal Article
Recenzirano
The upgraded DO detector at the Fermilab Tevatron will feature a new three-level trigger based on physics object recognition. The Level-2 muon trigger is required to use the timing data from the muon ...wire chambers and scintillator to rind track segments and then match those segments with Level-1 muon and fiber tracker trigger information. To accomplish this task, the Level-2 muon trigger features a three-stage approach. The first stage uses a parallel set of custom VME cards that route data through a high-speed and configurable bus to a series of 200-MHz Texas Instruments digital signal processors. This will reduce the large data volume distributed over some 140 sources to a manageable set of three-dimensional track stubs from the 16 cards. Data from these boards are combined to form muon track candidates in the second stage using another custom board built around a 500-MHz Compaq Alpha processor chip. In the third stage, another Alpha-based board matches the muon tracks with tracks found in the central tracking trigger and is able to correlate those muons with other physics objects in the event, such as jets. Queueing simulations of the system running at a rate consistent with the expected input rate and desired background rejection have shown that the Level-2 muon trigger will produce a dead time less than 5%.
Electron and photon identification in the Do experiment Augsten, K.; Avila, C.; Bandurin, D. V. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
06/2014, Letnik:
750
Journal Article
Recenzirano
Odprti dostop
The electron and photon reconstruction and identification algorithms used by the DO Collaboration at the Fermilab Tevatron collider are described. The determination of the electron energy scale and ...resolution is presented. Studies of the performance of the electron and photon reconstruction and identification are summarized. The results are based on measurements of Z boson decay events of Z ee and Z gamma ll(i=e mu) collected in pp(over bar) collisions at a center- of- mass energy of 1.96 TeV using an integrated luminosity of up to10 fb(-1.)
We present a measurement of top quark polarization in t ¯ t pair production in p ¯ p collisions at √ s = 1.96 TeV using data corresponding to 9.7 fb -1 of integrated luminosity recorded with the D0 ...detector at the Fermilab Tevatron Collider. We consider final states containing a lepton and at least three jets. The polarization is measured through the distribution of lepton angles along three axes: the beam axis, the helicity axis, and the transverse axis normal to the t ¯ t production plane. This is the first measurement of top quark polarization at the Tevatron using lepton + jet final states and the first measurement of the transverse polarization in t ¯ t production. The observed distributions are consistent with standard model predictions of nearly no polarization.
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