Publications by authors named "A Ari Hakimi"

284 Publications

Measurements of the Electroweak Diboson Production Cross Sections in Proton-Proton Collisions at sqrt[s]=5.02  TeV Using Leptonic Decays.

Phys Rev Lett 2021 Nov;127(19):191801

Universiteit Antwerpen, Antwerpen, Belgium.

The first measurements of diboson production cross sections in proton-proton interactions at a center-of-mass energy of 5.02 TeV are reported. They are based on data collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 302  pb^{-1}. Events with two, three, or four charged light leptons (electrons or muons) in the final state are analyzed. The WW, WZ, and ZZ total cross sections are measured as σ_{WW}=37.0_{-5.2}^{+5.5}(stat)_{-2.6}^{+2.7}(syst)  pb, σ_{WZ}=6.4_{-2.1}^{+2.5}(stat)_{-0.3}^{+0.5}(syst)  pb, and σ_{ZZ}=5.3_{-2.1}^{+2.5}(stat)_{-0.4}^{+0.5}(syst)  pb. All measurements are in good agreement with theoretical calculations at combined next-to-next-to-leading order quantum chromodynamics and next-to-leading order electroweak accuracy.
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http://dx.doi.org/10.1103/PhysRevLett.127.191801DOI Listing
November 2021

Combined searches for the production of supersymmetric top quark partners in proton-proton collisions at .

Eur Phys J C Part Fields 2021 3;81(11):970. Epub 2021 Nov 3.

Universiteit Antwerpen, Antwerpen, Belgium.

A combination of searches for top squark pair production using proton-proton collision data at a center-of-mass energy of 13 at the CERN LHC, corresponding to an integrated luminosity of 137 collected by the CMS experiment, is presented. Signatures with at least 2 jets and large missing transverse momentum are categorized into events with 0, 1, or 2 leptons. New results for regions of parameter space where the kinematical properties of top squark pair production and top quark pair production are very similar are presented. Depending on the model, the combined result excludes a top squark mass up to 1325 for a massless neutralino, and a neutralino mass up to 700 for a top squark mass of 1150 . Top squarks with masses from 145 to 295 , for neutralino masses from 0 to 100 , with a mass difference between the top squark and the neutralino in a window of 30 around the mass of the top quark, are excluded for the first time with CMS data. The results of theses searches are also interpreted in an alternative signal model of dark matter production via a spin-0 mediator in association with a top quark pair. Upper limits are set on the cross section for mediator particle masses of up to 420 .
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http://dx.doi.org/10.1140/epjc/s10052-021-09721-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8566447PMC
November 2021

Precision luminosity measurement in proton-proton collisions at in 2015 and 2016 at CMS.

Eur Phys J C Part Fields 2021 9;81(9):800. Epub 2021 Sep 9.

Universiteit Antwerpen, Antwerp, Belgium.

The measurement of the luminosity recorded by the CMS detector installed at LHC interaction point 5, using proton-proton collisions at in 2015 and 2016, is reported. The absolute luminosity scale is measured for individual bunch crossings using beam-separation scans (the van der Meer method), with a relative precision of 1.3 and 1.0% in 2015 and 2016, respectively. The dominant sources of uncertainty are related to residual differences between the measured beam positions and the ones provided by the operational settings of the LHC magnets, the factorizability of the proton bunch spatial density functions in the coordinates transverse to the beam direction, and the modeling of the effect of electromagnetic interactions among protons in the colliding bunches. When applying the van der Meer calibration to the entire run periods, the integrated luminosities when CMS was fully operational are 2.27 and 36.3 in 2015 and 2016, with a relative precision of 1.6 and 1.2%, respectively. These are among the most precise luminosity measurements at bunched-beam hadron colliders.
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http://dx.doi.org/10.1140/epjc/s10052-021-09538-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8550658PMC
September 2021

Search for a heavy vector resonance decaying to a  boson and a Higgs boson in proton-proton collisions at .

Eur Phys J C Part Fields 2021 3;81(8):688. Epub 2021 Aug 3.

Universiteit Antwerpen, Antwerp, Belgium.

A search is presented for a heavy vector resonance decaying into a boson and the standard model Higgs boson, where the boson is identified through its leptonic decays to electrons, muons, or neutrinos, and the Higgs boson is identified through its hadronic decays. The search is performed in a Lorentz-boosted regime and is based on data collected from 2016 to 2018 at the CERN LHC, corresponding to an integrated luminosity of 137 . Upper limits are derived on the production of a narrow heavy resonance , and a mass below 3.5 and 3.7 is excluded at 95% confidence level in models where the heavy vector boson couples predominantly to fermions and to bosons, respectively. These are the most stringent limits placed on the Heavy Vector Triplet model to date. If the heavy vector boson couples exclusively to standard model bosons, upper limits on the product of the cross section and branching fraction are set between 23 and 0.3 for a mass between 0.8 and 4.6 , respectively. This is the first limit set on a heavy vector boson coupling exclusively to standard model bosons in its production and decay.
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http://dx.doi.org/10.1140/epjc/s10052-021-09348-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8550580PMC
August 2021

Search for charged Higgs bosons produced in vector boson fusion processes and decaying into vector boson pairs in proton-proton collisions at .

Eur Phys J C Part Fields 2021 11;81(8):723. Epub 2021 Aug 11.

Universiteit Antwerpen, Antwerp, Belgium.

A search for charged Higgs bosons produced in vector boson fusion processes and decaying into vector bosons, using proton-proton collisions at at the LHC, is reported. The data sample corresponds to an integrated luminosity of 137 collected with the CMS detector. Events are selected by requiring two or three electrons or muons, moderate missing transverse momentum, and two jets with a large rapidity separation and a large dijet mass. No excess of events with respect to the standard model background predictions is observed. Model independent upper limits at 95% confidence level are reported on the product of the cross section and branching fraction for vector boson fusion production of charged Higgs bosons as a function of mass, from 200 to 3000 . The results are interpreted in the context of the Georgi-Machacek model.
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http://dx.doi.org/10.1140/epjc/s10052-021-09472-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8550626PMC
August 2021
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