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Search for long-lived particles decaying in the CMS endcap muon detectors in proton-proton collisions at $\sqrt{s} = $ 13 TeV

Armen Tumasyan, Wolfgang Adam, Janik Walter Andrejkovic, Thomas Bergauer, Suman Chatterjee, Marko Dragicevic, Alberto Escalante Del Valle, Rudolf Fruehwirth, Manfred Jeitler, Natascha Krammer, Lukas Lechner, Dietrich Liko (+2354 others)
2021 Physical review letters 127(26)  
A search for long-lived particles (LLPs) produced in decays of standard model (SM) Higgs bosons is presented. The data sample consists of 137 fb$^{-1}$ of proton-proton collisions at $\sqrt{s} =$ 13 TeV, recorded at the LHC in 2016-2018. A novel technique is employed to reconstruct decays of LLPs in the endcap muon detectors. The search is sensitive to a broad range of LLP decay modes and to masses as low as a few GeV. No excess of events above the SM background is observed. The most stringent
more » ... imits to date on the branching fraction of the Higgs boson to LLPs subsequently decaying to quarks and $\tau^+\tau^-$ are found for proper decay lengths greater than 6, 20, and 40 m, for LLP masses of 7, 15, and 40 GeV, respectively.
doi:10.3204/pubdb-2022-00238 fatcat:cfvh4j2wxbce5lnd33tz4e6rde

Observation of a New Excited Beauty Strange Baryon Decaying to$\Xi^-_\mathrm{b} \pi^+ \pi^-$

Albert M. Sirunyan, Armen Tumasyan, Wolfgang Adam, Janik Walter Andrejkovic, Thomas Bergauer, Suman Chatterjee, Marko Dragicevic, Alberto Escalante Del Valle, Rudolf Fruehwirth, Manfred Jeitler, Natascha Krammer, Lukas Lechner (+2354 others)
2021 Physical review letters 126(25)  
The Ξ − b π þ π − invariant mass spectrum is investigated with an event sample of proton-proton collisions at ffiffi ffi s p ¼ 13 TeV, collected by the CMS experiment at the LHC in 2016-2018 and corresponding to an integrated luminosity of 140 fb −1 . The ground state Ξ − b is reconstructed via its decays to J=ψΞ − and J=ψΛK MeV, where the last uncertainty reflects the precision of the Ξ − b baryon mass. The upper limit on the Ξ b ð6100Þ − natural width is determined to be 1.9 MeV at 95%
more » ... nce level. The low Ξ b ð6100Þ − signal yield observed in data does not allow a measurement of the quantum numbers of the new state. However, following analogies with the established excited Ξ c baryon states, the new Ξ b ð6100Þ − resonance and its decay sequence are consistent with the orbitally excited Ξ − b baryon, with spin and parity quantum numbers J P ¼ 3=2 − .
doi:10.18154/rwth-2021-10773 fatcat:jebivqmfpvgxbb7odn7phd5am4

Search for Long-Lived Particles Decaying in the CMS End Cap Muon Detectors in Proton-Proton Collisions at $\sqrt s$ =13 TeV

Armen Tumasyan, Wolfgang Adam, Janik Walter Andrejkovic, Thomas Bergauer, Suman Chatterjee, Marko Dragicevic, Alberto Escalante Del Valle, Rudolf Fruehwirth, Manfred Jeitler, Natascha Krammer, Lukas Lechner, Dietrich Liko (+2354 others)
2021 Physical review letters 127(26)  
A search for long-lived particles (LLPs) produced in decays of standard model (SM) Higgs bosons is presented. The data sample consists of 137 fb −1 of proton-proton collisions at ffiffi ffi s p ¼ 13 TeV, recorded at the LHC in 2016-2018. A novel technique is employed to reconstruct decays of LLPs in the end cap muon detectors. The search is sensitive to a broad range of LLP decay modes and to masses as low as a few GeV. No excess of events above the SM background is observed. The most stringent
more » ... limits to date on the branching fraction of the Higgs boson to LLPs subsequently decaying to quarks and τ þ τ − are found for proper decay lengths greater than 6, 20, and 40 m, for LLP masses of 7, 15, and 40 GeV, respectively.
doi:10.18154/rwth-2022-01524 fatcat:vy4sp662pnacvi5jigotju5tki

Constraints on the Initial State of Pb-Pb Collisions via Measurements of $Z$-Boson Yields and Azimuthal Anisotropy at $\sqrt {s_{NN}}$=5.02 TeV

Albert M. Sirunyan, Armen Tumasyan, Wolfgang Adam, Federico Ambrogi, Thomas Bergauer, Marko Dragicevic, Janos Erö, Alberto Escalante Del Valle, Rudolf Fruehwirth, Manfred Jeitler, Natascha Krammer, Lukas Lechner (+2333 others)
2021 Physical review letters 127(10)  
doi:10.18154/rwth-2021-09930 fatcat:en4xeka2bbhohmvzb5ndftqfby

Evidence for X(3872) in Pb-Pb Collisions and Studies of its Prompt Production at $\sqrt {s_{NN}}$=5.02 TeV

Albert M. Sirunyan, Armen Tumasyan, Wolfgang Adam, Federico Ambrogi, Thomas Bergauer, Marko Dragicevic, Janos Erö, Alberto Escalante Del Valle, Martin Flechl, Rudolf Fruehwirth, Manfred Jeitler, Natascha Krammer (+2297 others)
2022 Physical review letters 128(3)  
The first evidence for X(3872) production in relativistic heavy ion collisions is reported. The X(3872) production is studied in lead-lead (Pb-Pb) collisions at a center-of-mass energy of ffiffiffiffiffiffiffi ffi s NN p ¼ 5.02 TeV per nucleon pair, using the decay chain Xð3872Þ The data were recorded with the CMS detector in 2018 and correspond to an integrated luminosity of 1.7 nb −1 . The measurement is performed in the rapidity and transverse momentum ranges jyj < 1.6 and 15 < p T < 50
more » ... . The significance of the inclusive X(3872) signal is 4.2 standard deviations. The prompt X(3872) to ψ2S yield ratio is found to be ρ Pb-Pb ¼ 1.08 AE 0.49ðstatÞ AE 0.52ðsystÞ, to be compared with typical values of 0.1 for pp collisions. This result provides a unique experimental input to theoretical models of the X(3872) production mechanism, and of the nature of this exotic state.
doi:10.18154/rwth-2022-01812 fatcat:cxr6lwqqyjhhrfpbxh4zybiz74

Observation of Forward Neutron Multiplicity Dependence of Dimuon Acoplanarity in Ultraperipheral Pb-Pb Collisions at $\sqrt{s_{NN}}$=5.02 TeV

Albert M. Sirunyan, Armen Tumasyan, Wolfgang Adam, Thomas Bergauer, Marko Dragicevic, Janos Erö, Alberto Escalante Del Valle, Rudolf Fruehwirth, Manfred Jeitler, Natascha Krammer, Lukas Lechner, Dietrich Liko (+2345 others)
2021 Physical review letters 127(12)  
doi:10.18154/rwth-2021-11208 fatcat:nrsfo45lqnhv5b5in2omxfahwq

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

Armen Tumasyan, Wolfgang Adam, Janik Walter Andrejkovic, Thomas Bergauer, Suman Chatterjee, Marko Dragicevic, Alberto Escalante Del Valle, Rudolf Fruehwirth, Manfred Jeitler, Natascha Krammer, Lukas Lechner, Dietrich Liko (+2354 others)
2021 Physical review letters 127(19)  
The first measurements of diboson production cross sections in proton-proton interactions at a center-ofmass 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 ¼ 37:0 þ5.5 −5.2 ðstatÞ þ2.7 −2.6 ðsystÞ pb, σ WZ ¼ 6.4 þ2.5
more » ... ðstatÞ þ0.5 −0.3 ðsystÞ pb, and σ ZZ ¼ 5.3 þ2.5 −2.1 ðstatÞ þ0.5 −0.4 ðsystÞ 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.
doi:10.18154/rwth-2022-00263 fatcat:fmjtnz4jy5fzpn6wi46xnhmjhq

Measurement of the inclusive and differential Higgs boson production cross sections in the decay mode to a pair of $\tau$ leptons in pp collisions at $\sqrt{s} = $ 13 TeV

Armen Tumasyan, Wolfgang Adam, Janik Walter Andrejkovic, Thomas Bergauer, Suman Chatterjee, Marko Dragicevic, Alberto Escalante Del Valle, Rudolf Fruehwirth, Manfred Jeitler, Natascha Krammer, Lukas Lechner, Dietrich Liko (+2350 others)
2022 Physical review letters : PRL 128(8)  
leading order with the MLM jet matching and merging scheme [24] for the simulation of data taken in 2016 (2017 and 2018). It is also used to model the diboson production at NLO in (α S ), whereas POWHEG 2.0 and 1.0 are used for t t and single top quark production, respectively. Single top quark production in the t-channel and diboson events are normalized to their cross sections at NLO precision or higher [25, 26] . Drell-Yan events, as well as t t events and single top quark production in the
more » ... W channel, are normalized to their cross sections at NNLO precision [27, 28] . The generators are interfaced with PYTHIA8.212 [29] to model the parton showering and fragmentation, as well as the decay of the τ leptons. The PYTHIA tunes CUETP8M1 and CUETP8M4 [30] are used in simulation corresponding to the 2016 data-taking conditions, and the CP5 tune [31] is used for 2017 and 2018 simulations. The parton density function (PDF) set is NNPDF3.0 for 2016 simulations, and NNPDF 3.1 for 2017 and 2018 simulations [32] [33] [34] . Additional proton-proton interactions per bunch crossing, called pileup, are added to the simulations with the profile observed in data. Simulated events are processed through a GEANT4 [35] simulation of the CMS detector. The particle-flow (PF) algorithm [36] is used to reconstruct the events on the basis of information from the different CMS subdetectors. Muons are reconstructed from tracks and hits in the tracker and muon systems [37, 38] . Electrons are reconstructed from tracks in the tracking system and calorimeter deposits, and identified with a multivariate discriminant described in Ref. [39] . The relative isolation of electrons (muons) is calculated on the basis of the p T of tracks in a cone of ΔR ¼ ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ffi ðΔηÞ 2 þ ðΔϕÞ 2 p < 0.3 (0.4) centered on the lepton track, corrected for charged and neutral pileup contributions; it is required to be less than 0.15. Jets are clustered from PF candidates using the anti-(k T ) FASTJET algorithm with distance parameter R of 0.4 [40, 41], requiring p T > 30 GeV and jηj < 4.7. Jet energy corrections are applied on an event-by-event basis [36, 42, 43]. In events collected in 2017, jets with p T < 50 GeV and 2.65 < jηj < 3.14 are discarded to eliminate spurious jets caused by detector noise. Hadronic jets originating from b quarks are tagged
doi:10.18154/rwth-2022-03903 fatcat:wimvbnpqb5gstcqo5aiyueyhpq

Search for long-lived particles produced in association with a Z boson in proton-proton collisions at $ \sqrt{s} $ = 13 TeV

Armen Tumasyan, Wolfgang Adam, Janik Walter Andrejkovic, Thomas Bergauer, Suman Chatterjee, Marko Dragicevic, Alberto Escalante Del Valle, Rudolf Fruehwirth, Manfred Jeitler, Natascha Krammer, Lukas Lechner, Dietrich Liko (+2360 others)
2022 Journal of high energy physics : JHEP 2022(3)  
A search for long-lived particles (LLPs) produced in association with a Z boson is presented. The study is performed using data from proton-proton collisions with a center-of-mass energy of 13 TeV recorded by the CMS experiment during 2016-2018, corresponding to an integrated luminosity of 117 fb −1 . The LLPs are assumed to decay to a pair of standard model quarks that are identified as displaced jets within the CMS tracker system. Triggers and selections based on Z boson decays to electron or
more » ... muon pairs improve the sensitivity to light LLPs (down to 15 GeV). This search provides sensitivity to beyond the standard model scenarios which predict LLPs produced in association with a Z boson. In particular, the results are interpreted in the context of exotic decays of the Higgs boson to a pair of scalar LLPs (H → SS). The Higgs boson decay branching fraction is constrained to values less than 6% for proper decay lengths of 10-100 mm and for LLP masses between 40 and 55 GeV. In the case of low-mass (≈ 15 GeV) scalar particles that subsequently decay to a pair of b quarks, the search is sensitive to branching fractions B(H → SS) < 20% for proper decay lengths of 10-50 mm. The use of associated production with a Z boson increases the sensitivity to low-mass LLPs of this analysis with respect to gluon fusion searches. In the case of 15 GeV scalar LLPs, the improvement corresponds to a factor of 2 at a proper decay length of 30 mm.
doi:10.18154/rwth-2022-04119 fatcat:lvuxj2rhvfbyjaaupgjw5cbbna

Using Z Boson Events to Study Parton-Medium Interactions in Pb-Pb Collisions

Albert M. Sirunyan, Armen Tumasyan, Wolfgang Adam, Federico Ambrogi, Thomas Bergauer, Marko Dragicevic, Janos Erö, Alberto Escalante Del Valle, Rudolf Fruehwirth, Manfred Jeitler, Natascha Krammer, Lukas Lechner (+2340 others)
2022 Physical review letters : PRL 128(12)  
doi:10.18154/rwth-2022-05323 fatcat:huzghgldwzczzpvv7ckvqitc6u

Measurement of the inclusive $ \mathrm{t}\overline{\mathrm{t}} $ production cross section in proton-proton collisions at $ \sqrt{s} $ = 5.02 TeV

Armen Tumasyan, Wolfgang Adam, Janik Walter Andrejkovic, Thomas Bergauer, Suman Chatterjee, Marko Dragicevic, Alberto Escalante Del Valle, Rudolf Fruehwirth, Manfred Jeitler, Natascha Krammer, Lukas Lechner, Dietrich Liko (+2355 others)
2022 Journal of high energy physics (4)  
The top quark pair production cross section is measured in proton-proton collisions at a center-of-mass energy of 5.02 TeV. The data were collected in a special LHC low-energy and low-intensity run in 2017, and correspond to an integrated luminosity of 302 pb −1 . The measurement is performed using events with one electron and one muon of opposite charge, and at least two jets. The measured cross section is 60.7 ± 5.0 (stat) ± 2.8 (syst) ± 1.1 (lumi) pb. A combination with the result in the
more » ... le lepton + jets channel, based on data collected in 2015 at the same center-of-mass energy and corresponding to an integrated luminosity of 27.4 pb −1 , is then performed. The resulting measured value is 63.0 ± 4.1 (stat) ± 3.0 (syst+lumi) pb, in agreement with the standard model prediction of 66.8 +2.9 −3.1 pb.
doi:10.18154/rwth-2022-05828 fatcat:63khg7mli5dwdbsqf5zh3k2pfi

Search for strongly interacting massive particles generating trackless jets in proton–proton collisions at $\sqrt{s} = 13\,\text {TeV}$

Armen Tumasyan, Wolfgang Adam, Thomas Bergauer, Marko Dragicevic, Janos Erö, Alberto Escalante Del Valle, Rudolf Fruehwirth, Manfred Jeitler, Natascha Krammer, Lukas Lechner, Dietrich Liko, Ivan Mikulec (+2346 others)
2022 The European physical journal / C 82(3)  
A search for dark matter in the form of strongly interacting massive particles (SIMPs) using the CMS detector at the LHC is presented. The SIMPs would be produced in pairs that manifest themselves as pairs of jets without tracks. The energy fraction of jets carried by charged particles is used as a key discriminator to suppress efficiently the large multijet background, and the remaining background is estimated directly from data. The search is performed using proton-proton collision data
more » ... ponding to an integrated luminosity of 16.1 fb −1 , collected with the CMS detector in 2016. No significant excess of events is observed above the expected background. For the simplified dark matter model under consideration, SIMPs with masses up to 100 GeV are excluded and further sensitivity is explored towards higher masses.
doi:10.18154/rwth-2022-03904 fatcat:lt5yal6kercy5fy2k2sbint6um

Measurements of angular distance and momentum ratio distributions in three-jet and Z + two-jet final states in pp collisions

Albert M. Sirunyan, Armen Tumasyan, Wolfgang Adam, Thomas Bergauer, Marko Dragicevic, Janos Erö, Alberto Escalante Del Valle, Rudolf Fruehwirth, Manfred Jeitler, Natascha Krammer, Lukas Lechner, Dietrich Liko (+2338 others)
2021 The European physical journal / C 81(9)  
Collinear (small-angle) and large-angle, as well as soft and hard radiations are investigated in three-jet and Z + two-jet events collected in proton-proton collisions at the LHC. The normalized production cross sections are measured as a function of the ratio of transverse momenta of two jets and their angular separation. The measurements in the three-jet and Z + two-jet events are based on data collected at a center-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.8 fb
more » ... −1 . The Z + two-jet events are reconstructed in the dimuon decay channel of the Z boson. The three-jet measurement is extended to include √ s = 13 TeV data corresponding to an integrated luminosity of 2.3 fb −1 . The results are compared to predictions from event generators that include parton showers, multiple parton interactions, and hadronization. The collinear and soft regions are in general well described by parton showers, whereas the regions of large angular separation are often best described by calculations using higher-order matrix elements.
doi:10.18154/rwth-2021-10599 fatcat:dj7woj4vgrb3ja77hxcjh6biuq

Fragmentation of jets containing a prompt J/ψ meson in PbPb and pp collisions at $ \sqrt{sNN} $=5.02TeV

Armen Tumasyan, Wolfgang Adam, Thomas Bergauer, Marko Dragicevic, Janos Erö, Alberto Escalante Del Valle, Rudolf Fruehwirth, Manfred Jeitler, Natascha Krammer, Lukas Lechner, Dietrich Liko, Thomas Madlener (+2337 others)
2022 Physics letters / B 825  
Jets containing a prompt J/ψ meson are studied in lead-lead collisions at a nucleon-nucleon center-ofmass energy of 5.02 TeV, using the CMS detector at the LHC. Jets are selected to be in the transverse momentum range of 30 < p T < 40 GeV. The J/ψ yield in these jets is evaluated as a function of the jet fragmentation variable z, the ratio of the J/ψ p T to the jet p T . The nuclear modification factor, R AA , is then derived by comparing the yield in lead-lead collisions to the corresponding
more » ... pectation based on proton-proton data, at the same nucleon-nucleon center-of-mass energy. The suppression of the J/ψ yield shows a dependence on z, indicating that the interaction of the J/ψ with the quark-gluon plasma formed in heavy ion collisions depends on the fragmentation that gives rise to the J/ψ meson.
doi:10.18154/rwth-2022-04838 fatcat:zo3uxryxqff7peiuzi4co4rc2a

Fragmentation of jets containing a prompt J$/\psi$ meson in PbPb and pp collisions at $\sqrt{s_\mathrm{NN}} =$ 5.02 TeV

Armen Tumasyan, Wolfgang Adam, Thomas Bergauer, Marko Dragicevic, Janos Erö, Alberto Escalante Del Valle, Rudolf Fruehwirth, Manfred Jeitler, Natascha Krammer, Lukas Lechner, Dietrich Liko, Thomas Madlener (+2337 others)
2022 Physics letters / B 825  
Jets containing a prompt J$/\psi$ meson are studied in lead-lead collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV, using the CMS detector at the LHC. Jets are selected to be in the transverse momentum range of 30 $\lt p_\mathrm{T} \lt$ 40 GeV. The J$/\psi$ yield in these jets is evaluated as a function of the jet fragmentation variable $z$, the ratio of the J$/\psi$$p_\mathrm{T} $ to the jet $p_\mathrm{T}$. The nuclear modification factor, $R_\mathrm{AA}$, is then derived by
more » ... paring the yield in lead-lead collisions to the corresponding expectation based on proton-proton data, at the same nucleon-nucleon center-of-mass energy. The suppression of the J$/\psi$ yield shows a dependence on $z$, indicating that the interaction of the J$/\psi$ with the quark-gluon plasma formed in heavy ion collisions depends on the fragmentation that gives rise to the J$/\psi$ meson.
doi:10.3204/pubdb-2022-00235 fatcat:wcnsn63g5fbw7fyra5ia66xrgi
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