Baida Achkar - Academia.edu (original) (raw)

Papers by Baida Achkar

CERN-LHC. Studies of the fragmentation of jets into charged particles in heavy-ion collisions can... more CERN-LHC. Studies of the fragmentation of jets into charged particles in heavy-ion collisions can provide information about the mechanism of jet-quenching by the hot and dense QCD matter created in such collisions, the quark-gluon plasma. This paper presents a measurement of the angular distribution of charged particles around the jet axis in sNN=5.02 TeV Pb+Pb and pp collisions, using the ATLAS detector at the LHC. The Pb+Pb and pp data sets have integrated luminosities of 0.49 nb−1 and 25 pb−1, respectively. The measurement is performed for jets reconstructed with the anti-kt algorithm with radius parameter R=0.4 and is extended to an angular distance of r=0.8 from the jet axis. Results are presented as a function of Pb+Pb collision centrality and distance from the jet axis for charged particles with transverse momenta in the 1−63 GeV range, matched to jets with transverse momenta in the 126−316 GeV range and an absolute value of jet rapidity of less than 1.7. Modifications to the...

Four lepton mass full run II measurement and SM prediction. ATLAS internal.

Nuclear Physics A, 2019

Measurement of angular and momentum distributions of charged particles within and around jets in ... more Measurement of angular and momentum distributions of charged particles within and around jets in Pb+Pb and p p collisions at √ s NN = 5.02 TeV with the ATLAS detector The ATLAS Collaboration Studies of the fragmentation of jets into charged particles in heavy-ion collisions can provide information about the mechanism of jet-quenching by the hot and dense QCD matter created in such collisions, the quark-gluon plasma. This paper presents a measurement of the angular distribution of charged particles around the jet axis in √ s NN = 5.02 TeV Pb+Pb and pp collisions, using the ATLAS detector at the LHC. The Pb+Pb and pp data sets have integrated luminosities of 0.49 nb −1 and 25 pb −1 , respectively. The measurement is performed for jets reconstructed with the anti-k t algorithm with radius parameter R = 0.4 and is extended to an angular distance of r = 0.8 from the jet axis. Results are presented as a function of Pb+Pb collision centrality and distance from the jet axis for charged particles with transverse momenta in the 1-63 GeV range, matched to jets with transverse momenta in the 126-316 GeV range and an absolute value of jet rapidity of less than 1.7. Modifications to the measured distributions are quantified by taking a ratio to the measurements in pp collisions. Yields of charged particles with transverse momenta below 4 GeV are observed to be increasingly enhanced as a function of angular distance from the jet axis, reaching a maximum at r = 0.6. Charged particles with transverse momenta above 4 GeV have an enhanced yield in Pb+Pb collisions in the jet core for angular distances up to r = 0.05 from the jet axis, with a suppression at larger distances.

$Research paper thumbnail of Search for type-III seesaw heavy leptons in dilepton final states in pp collisions at <math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><semantics><mrow><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>13</mn><mtext> </mtext><mtext>TeV</mtext></mrow><annotation encoding="application/x-tex">\sqrt{s} = 13\,{\text {TeV}}</annotation></semantics></math>s<svg xmlns="http://www.w3.org/2000/svg" width='400em' height='1.08em' viewBox='0 0 400000 1080' preserveAspectRatio='xMinYMin slice'><path d='M95,702 c-2.7,0,-7.17,-2.7,-13.5,-8c-5.8,-5.3,-9.5,-10,-9.5,-14 c0,-2,0.3,-3.3,1,-4c1.3,-2.7,23.83,-20.7,67.5,-54 c44.2,-33.3,65.8,-50.3,66.5,-51c1.3,-1.3,3,-2,5,-2c4.7,0,8.7,3.3,12,10 s173,378,173,378c0.7,0,35.3,-71,104,-213c68.7,-142,137.5,-285,206.5,-429 c69,-144,104.5,-217.7,106.5,-221 l0 -0 c5.3,-9.3,12,-14,20,-14 H400000v40H845.2724 s-225.272,467,-225.272,467s-235,486,-235,486c-2.7,4.7,-9,7,-19,7 c-6,0,-10,-1,-12,-3s-194,-422,-194,-422s-65,47,-65,47z M834 80h400000v40h-400000z'/></svg>=13TeV with the ATLAS detector$

The European Physical Journal C, 2021

A search for the pair production of heavy leptons as predicted by the type-III seesaw mechanism i... more A search for the pair production of heavy leptons as predicted by the type-III seesaw mechanism is presented. The search uses proton–proton collision data at a centre-of-mass energy of 13 TeV, corresponding to 139,textfb−1139\,{\text {fb}}^{-1}139,textfb−1 139 fb - 1 of integrated luminosity recorded by the ATLAS detector during Run 2 of the Large Hadron Collider. The analysis focuses on the final state with two light leptons (electrons or muons) of different flavour and charge combinations, with at least two jets and large missing transverse momentum. No significant excess over the Standard Model expectation is observed. The results are translated into exclusion limits on heavy-lepton masses, and the observed lower limit on the mass of the type-III seesaw heavy leptons is 790 GeV at 95% confidence level.

The results of a search for gluino and squark pair production pp decaying via charginos to a fina... more The results of a search for gluino and squark pair production pp decaying via charginos to a final state consisting of a W boson, the lightest neutralino, and quarks are presented. The signal is characterized by the presence of a single charged lepton from a W boson decay, jets, and missing transverse momentum. The analysis was performed using proton-proton collision data taken at a center-of-mass energy sqrts\sqrt{s}sqrts = 13 TeV provided by the Large Hadron Collider and recorded by the ATLAS experiment, corresponding to 139 fb$^{-1}$. No statistically significant excess of events above the Standard Model expectation is found. Limits are set on the direct production of squarks and gluino in the simplified models, masses of up to 2.2 TeV (1.4 TeV) are excluded at 95% confidence level.

Four lepton mass full run II measurement and SM prediction. ATLAS internal.

Nuclear Physics A, 2019

The European Physical Journal C, 2021