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Differential top-antitop cross-section measurements as a function of observables constructed from final-state particles using pp collisions at √s=7 TeV in the ATLAS detector
A
bstract
Various differential cross-sections are measured in top-quark pair
t
t
¯
events produced in proton-proton collisions at a centre-of-mass energy of
s
=
7
TeV at the LHC with the ATLAS detector. These differential cross-sections are presented in a data set corresponding to an integrated luminosity of 4
.
6 fb
−1
. The differential cross-sections are presented in terms of kinematic variables, such as momentum, rapidity and invariant mass, of a top-quark proxy referred to as the pseudo-top-quark as well as the pseudo-top-quark pair system. The dependence of the measurement on theoretical models is minimal.
The measurements are performed on
t
t
¯
events in the lepton+jets channel, requiring exactly one charged lepton and at least four jets with at least two of them tagged as originating from a
b
-quark. The hadronic and leptonic pseudo-top-quarks are defined via the leptonic or hadronic decay mode of the
W
boson produced by the top-quark decay in events with a single charged lepton. Differential cross-section measurements of the pseudo-top-quark variables are compared with several Monte Carlo models that implement next-to-leading order or leading-order multi-leg matrix-element calculations.
Journal Article
Drawing mechanisms for top coal in longwall top coal caving (LTCC): A review of two decades of literature
This review details the state of the art in research on top coal drawing mechanisms in Longwall
t
op
c
oal
c
aving (LTCC) by examining the relevant literature over the last two decades. It starts with an introduction of the brief history and basic procedures of LTCC. The framework of research on the drawing mechanism, basic concepts, and some theoretical models of LTCC are detailed in sect. research framework of top coal drawing mechanism. The authors note that the
T
op
c
oal
d
rawbody (TCD),
T
op
c
oal
b
oundary (TCB) and
T
op
c
oal
r
ecovery
r
atio (TCRR) are key factors in the drawing mechanism. The
B
ody–
b
oundary–
r
atio (BBR) research system has been the classic framework for research over the last 20 years. The modified Bergmark–Roos model, which considers the effects of the supporting rear canopy, flowing velocity of top coal, and its shape factor, is optimal for characterizing the TCD. A 3D model to describe the TCB that considers the thicknesses of the coal seam and roof strata is reviewed. In sect. physical testing and numerical simulation, the physical tests and numerical simulations in the literature are classified for ease of bibliographical review, and classic conclusions regarding the drawing mechanism of top coal are presented and discussed with elaborate illustrations and descriptions. The deflection of the TCD is noted, and is caused by the shape of the rear canopy. The inclined coal seam always induces a larger TCD, and a deflection in the TCD has also been observed in it. The effects of the drawing sequence and drawing interval on the TCRR are reviewed, where a long drawing interval is found to lead to significant loss of top coal. Its flowing behavior and velocity distribution are also presented. Sect. practical applications of drawing mechanisms for LTCC mines 4 summarizes over 10 cases where the TCRR of LTCC mines improved due to the guidance of the drawing mechanism. The final section provides a summary of the work here and some open questions. Prospective investigations are highlighted to give researchers guidance on promising issues in future research on LTCC.
Journal Article
Measurement of the top quark pair production charge asymmetry in proton-proton collisions at √s = 7 TeV using the ATLAS detector
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) Abstract This paper presents a measurement of the top quark pair (...) production charge asymmetry A ^sub C^ using 4.7 fb^sup -1^ of proton-proton collisions at a centre-of-mass energy ... = 7 TeV collected by the ATLAS detector at the LHC. A ...-enriched sample of events with a single lepton (electron or muon), missing transverse momentum and at least four high transverse momentum jets, of which at least one is tagged as coming from a b-quark, is selected. A likelihood fit is used to reconstruct the ... event kinematics. A Bayesian unfolding procedure is employed to estimate A ^sub C^ at the parton-level. The measured value of the ... production charge asymmetry is A ^sub C^ = 0.006 ± 0.010, where the uncertainty includes both the statistical and the systematic components. Differential A ^sub C^ measurements as a function of the invariant mass, the rapidity and the transverse momentum of the ... system are also presented. In addition, A ^sub C^ is measured for a subset of events with large ... velocity, where physics beyond the Standard Model could contribute. All measurements are consistent with the Standard Model predictions. [Figure not available: see fulltext.]
Journal Article
Measurement of the top-quark pole mass in dileptonic $t\\overline{t}$ + 1-jet events at $\\sqrt{s}=13$ TeV with the ATLAS experiment
A measurement of the top-quark pole mass $m$$^{pole}_{t}$ is presented in $t\\bar{t}$ events with an additional jet, $t\\bar{t}$+ 1-jet, produced in pp collisions at $\\sqrt{s} = 13 TeV. The data sample, recorded with the ATLAS experiment during Run 2 of the LHC, corresponds to an integrated luminosity of 140 fb−1. Events with one electron and one muon of opposite electric charge in the final state are selected to measure the $t\\bar{t}$ + 1-jet differential cross-section as a function of the inverse of the invariant mass of the $t\\bar{t}$ + 1-jet system. Iterative Bayesian Unfolding is used to correct the data to enable comparison with fixed-order calculations at next-to-leading-order accuracy in the strong coupling. The process pp → $t\\bar{t}$j(2 → 3), where top quarks are taken as stable particles, and the process pp → $b\\bar{b}$l+ vl–$\\overline{ν}$j (2 → 7), which includes top-quark decays to the dilepton final state and off-shell effects, are considered. The top-quark mass is extracted using a χ2 fit of the unfolded normalized differential cross-section distribution. The results obtained with the 2 → 3 and 2 → 7 calculations are compatible within theoretical uncertainties, providing an important consistency check.
Journal Article
Measurement of the charge asymmetry in dileptonic decays of top quark pairs in pp collisions at s√=7 TeV using the ATLAS detector
A
bstract
A measurement of the top-antitop
t
t
¯
charge asymmetry is presented using data corresponding to an integrated luminosity of 4.6 fb
−1
of LHC
pp
collisions at a centreof-mass energy of 7 TeV collected by the ATLAS detector. Events with two charged leptons, at least two jets and large missing transverse momentum are selected. Two observables are studied:
A
C
ℓℓ
based on the identified charged leptons, and
A
C
t
t
¯
, based on the reconstructed
tt
final state. The asymmetries are measured to be
A
C
ℓ
ℓ
=
0.024
±
0.015
stat
.
±
0.009
syst
.
,
A
C
t
t
¯
=
0.021
±
0.025
stat
.
±
0.017
syst
.
.
The measured values are in agreement with the Standard Model predictions.
Journal Article
Structure, function and regulation of the hsp90 machinery
Heat shock protein 90 (Hsp90) is an ATP-dependent molecular chaperone which is essential in eukaryotes. It is required for the activation and stabilization of a wide variety of client proteins and many of them are involved in important cellular pathways. Since Hsp90 affects numerous physiological processes such as signal transduction, intracellular transport, and protein degradation, it became an interesting target for cancer therapy. Structurally, Hsp90 is a flexible dimeric protein composed of three different domains which adopt structurally distinct conformations. ATP binding triggers directionality in these conformational changes and leads to a more compact state. To achieve its function, Hsp90 works together with a large group of cofactors, termed co-chaperones. Co-chaperones form defined binary or ternary complexes with Hsp90, which facilitate the maturation of client proteins. In addition, posttranslational modifications of Hsp90, such as phosphorylation and acetylation, provide another level of regulation. They influence the conformational cycle, co-chaperone interaction, and inter-domain communications. In this review, we discuss the recent progress made in understanding the Hsp90 machinery.
Journal Article
Differential cross section measurements for the production of top quark pairs and of additional jets using dilepton events from pp collisions at $\\sqrt{s}$ = 13 TeV
Differential cross sections for top quark pair ($\\textrm{t}\\overline{\\textrm{t}}$) production are measured in proton-proton collisions at a center-of-mass energy of 13 TeV using a sample of events containing two oppositely charged leptons. The data were recorded with the CMS detector at the CERN Large Hadron Collider and correspond to an integrated luminosity of 138 fb−1. The differential cross sections are measured as functions of kinematic observables of the $\\textrm{t}\\overline{\\textrm{t}}$ system, the top quark and antiquark and their decay products, as well as of the number of additional jets in the event. The results are presented as functions of up to three variables and are corrected to the parton and particle levels. When compared to standard model predictions based on quantum chromodynamics at different levels of accuracy, it is found that the calculations do not always describe the observed data. The deviations are found to be largest for the multi-differential cross sections.
Journal Article
Measurement of t¯t production in association withadditional b-jets in the eμ final state in proton–protoncollisions at √s = 13 TeV with the ATLAS detector
This paper presents measurements of top-antitop quark pair (t (t) over bar) production in association with additional b-jets. The analysis utilises 140 fb(-1) of proton-proton collision data collected with the ATLAS detector at the Large Hadron Collider at a centre-of-mass energy of 13TeV. Fiducial cross-sections are extracted in a final state featuring one electron and one muon, with at least three or four b-jets. Results are presented at the particle level for both integrated cross-sections and normalised differential cross-sections, as functions of global event properties, jet kinematics, and b-jet pair properties. Observable quantities characterising b-jets originating from the top quark decay and additional b-jets are also measured at the particle level, after correcting for detector effects. The measured integrated fiducial cross-sections are consistent with t (t) over barb (b) over bar predictions from various next-to-leading-order matrix element calculations matched to a parton shower within the uncertainties of the predictions. State-of-the-art theoretical predictions are compared with the differential measurements; none of them simultaneously describes all observables. Differences between any two predictions are smaller than the measurement uncertainties for most observables.
Journal Article
Measurement of production in association with additional b -jets in the eμ final state in proton–proton collisions at √s = 13 TeV with the ATLAS detector
This paper presents measurements of top-antitop quark pair (t¯t) production inassociation with additional b-jets. The analysis utilises 140 fb −1 of proton–proton collisiondata collected with the ATLAS detector at the Large Hadron Collider at a centre-of-massenergy of 13 TeV. Fiducial cross-sections are extracted in a final state featuring one electronand one muon, with at least three or four b-jets . Results are presented at the particle level forboth integrated cross-sections and normalised differential cross-sections, as functions of globalevent properties, jet kinematics, and b-jet pair properties. Observable quantities characterisingb-jets originating from the top quark decay and additional b-jets are also measured at theparticle level, after correcting for detector effects. The measured integrated fiducial cross-sections are consistent with t¯tb¯b predictions from various next-to-leading-order matrix elementcalculations matched to a parton shower within the uncertainties of the predictions. State-of-the-art theoretical predictions are compared with the differential measurements; none ofthem simultaneously describes all observables. Differences between any two predictions aresmaller than the measurement uncertainties for most observables.
Journal Article