Download or read book Search for Dark Matter Decaying to Two Displaced Muons Produced in Proton proton Collisions at 13 TeV with the CMS Detector and for Dark Photons Produced in Electron positron Fixed target Collisions at 500 MeV with the PADME Detector written by Andre Sterenberg Frankenthal and published by . This book was released on 2020 with total page 319 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two novel searches for dark matter using particle accelerators are presented. The first is a search for inelastically-coupled dark matter with the CMS detector at CERN, relying on 137 inverse femtobarns of proton-proton collision data collected at 13 TeV center-of-mass energy between 2016 and 2018. The search strategy exploits the striking signature expected of inelastic dark matter: a pair of displaced, soft, and narrow muons collimated with missing transverse momentum and recoiled off an initial-state radiation jet. This is the first search for inelastic dark matter at a hadron collider. The second experiment is PADME, a small-scale detector to search for dark photons located in Frascati, Italy. PADME seeks to detect the production of dark photons in positron-electron collisions with a stationary diamond target and a 500 MeV positron beam. The missing-mass technique employed in the experiment relies on constraining all four-momenta in the system except for the dark photon and looking for a bump in the resulting invariant mass distribution corresponding to the dark photon's mass. The projected sensitivity for both experiments is compared in the context of highlighting the need for a comprehensive experimental search program for dark matter. Both analyses expect first public results by the end of 2020.
Download or read book Searching for Dark Matter with the CMS Detector in Proton proton Collisions Containing a Single High pT Photon and Large E miss t written by Brandon Leigh Allen and published by . This book was released on 2019 with total page 165 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, we present a search for dark matter in final states containing a high- PT photon and large missing transverse momentum in proton-proton collisions at [square root of s] = 13 TeV using data collected by the Compact Muon Solenoid.(CMS) experiment at the CERN Large Hadron Collider (LHC) corresponding to an integrated luminosity of 35.9 inverse femtobarns. The main advances in experimental technique compared to previous searches in this final state are the use of data-driven control regions to constrain the main irreducible backgrounds from Z( --> vv̄ + [gamma] and W( --> [iota]v)+ [gamma] production and an in-depth study of the unique anomolous detector signatures that result in backgrounds due to non-collision processes. With these improvements, we have the most robust analysis of this kind presented to date. No deviations from the predictions of the standard model are observed. The results are interpreted in the context of dark matter production and limits on new physics parameters are calculated at 95% confidence level. We focus on two simplified dark matter production models where new vector and axial mediators couple a new dark dirac fermion to the Standard Model quarks. These models are chosen as they cover a large class of WIMP-like dark matter particles that show up in many types of more complete new physics models. For the two models considered, the observed (expected) lower limits on the masses of the new mediators are 950 (1150) GeV for a dark matter particle of a mass of 1 GeV.
Download or read book Search for the Decays of Stopped Exotic Long lived Particles Produced in P P Collisions at 13 TeV at CMS written by Weifeng Ji and published by . This book was released on 2018 with total page 112 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this dissertation, I present the searches looking for decays of stopped massive long-lived exotic particles, which are pair produced in the proton-proton collisions at 13 TeV and come to rest afterwards in the CMS detector at the CERN LHC. The decays are most likely to be observed when there are no collisions. Two specific decay scenarios are studied: a long-lived particle (LLP) decaying hadronically or semi- leptonically in the calorimeter, and a LLP decaying semi-leptonically or leptonically to a pair of muons in the muon detector. The calorimeter-based search is performed using 2.7 fb-1 of 13 TeV collision run data collected in 2015 and 35.9 fb-1 of 13 TeV collision run data collected in 2016, corresponding to a total trigger livetime of 721 hours. The muon search is performed using 2.8 fb-1 of 13 TeV collision run data collected in 2015 and 36.2 fb-1 of 13 TeV collision run data collected in 2016, corresponding to a total trigger livetime of 744 hours. Search results are interpreted in a couple of simplified models. The limits on the production cross sections and masses of LLPs are calculated as a function of particle lifetimes, which vary from 100 ns to 10 days, assuming the corresponding decaying branching fractions to be 100%. The results are the most stringent ones on the stopped LLPs so far.
Download or read book A Search for Long lived Particles that Stop in the CMS Detector and Decay to Muons written by and published by . This book was released on 2016 with total page 338 pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for long-lived particles that are produced in proton-proton collisions at the CERN LHC, come to rest in the CMS detector, and decay to muons is presented. The decays of the stopped particles could be observed during the intervals between LHC beam crossings, at times that are well separated from any proton-proton collisions. The analysis uses 19.7 1/fb of 8 TeV data collected by CMS in 2012, during a search interval of 293 hours of trigger livetime. Massive, long-lived particles do not exist in the Standard Model, and so any sign of them would be an indication of new physics. The results are interpreted with a model that predicts a long-lived particle that has a charge of twice the electron charge and that behaves like a lepton. Cross section limits are set for each long-lived particle mass as a function of lifetime, for lifetimes between 100 ns and 10 days. These are the first limits for long-lived stopped particles that decay to muons.
Download or read book A Collider Search for Dark Matter Produced in Association with a Higgs Boson with the CMS Detector at the 13 TeV LHC written by Dustin Ray Burns and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The study presented in this dissertation is a search for dark matter produced in 13 TeV proton-proton collisions at the Large Hadron Collider (LHC) using 35.9 fb−1 of data collected in 2016 with the Compact Muon Solenoid (CMS) detector. Dark matter escapes the detector without interacting, resulting in a large imbalance of transverse momentum, which can be observed when a Higgs boson is tagged in the opposite direction. A variety of models which motivate a dark matter and Higgs interaction are discussed. The experimental signature of these models is called mono-Higgs. In this search, the Higgs is produced primarily from gluon fusion and decays to four leptons via two Z bosons (H → ZZ → 4l). In addition to observing the Higgs in the four-lepton final state, an extensive study of missing transverse energy (MET) is required to search for the mono-Higgs signature. A background model is developed for the Standard Model processes that result in the same final state as the signal, then a counting experiment is performed in an optimized signal region. There is no evidence for an excess of events in the signal region above the backgrounds, so cross section limits are set for two kinematically distinct signal models.
Download or read book A Search for Dark Particles Produced in Association with the Z Boson and Jets in 13 TeV Proton Proton Collisions written by Bobak Taleb Hashemi and published by . This book was released on 2018 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents the results of a search for new physics in proton-proton collisions at the Large Hadron Collider, running with 13 TeV center of mass energy, using data gathered by the Compact Muon Solenoid (CMS). The search targets TeV mass-scale dark matter candidates and uses final states with two opposite-charge and same-flavor light leptons (electrons or muons) having dilepton mass consistent with the Z boson, at least 2 hadronic jets, and at least 100 GeV of transverse momentum imbalance. The thesis contains a historical introduction to particle physics, brief reviews of the standard model and supersymmetry, an in-depth discussion of the acquisition of data by the Large Hadron Collider and CMS detector, and a pedagogical overview of the analysis methods used. No statistically significant deviation is found from the expected standard model background. The search results are presented and interpreted in the context of several simplified models of supersymmetry, including a model of Gauge Mediated Supersymmetry-Breaking (GSMB) with gluino production and models with Electroweakino production. The excluded mass ranges for these models are advanced by approximately 50-100% with respect to the best previous searches. This work represents the current state of the art for their exclusion.
Download or read book Search for Dark Matter and Unparticles in Events with a Z Boson and Missing Transverse Momentum in Proton proton Collisions at Sqrt s written by and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for dark matter and unparticle production at the LHC has been performed using events containing two charged leptons (electrons or muons), consistent with the decay of a Z boson, and large missing transverse momentum. This study is based on data collected with the CMS detector in 2015, corresponding to an integrated luminosity of 2.3 inverse femtobarns of proton-proton collisions at the LHC, at a center-of-mass energy of 13 TeV. No excess over the standard model expectation is observed. Compared to previous searches in this topology, which exclusively relied on effective field theories, the results are interpreted in terms of a simplified model of dark matter production for both vector and axial vector couplings between a mediator and dark matter particles. The first study of this class of models using CMS data at sqrt(s)=13 TeV is presented. Additionally, effective field theories of dark matter and unparticle production are used to interpret the data.
Download or read book A Measurement of Wbb Production and a Search for Monophoton Signals of Dark Matter Using the CMS Detector at the CERN LHC written by Thomas Mastrianni Perry and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents the results of two analyses of data from proton-proton collisions collected by the CMS Collaboration at the CERN LHC during operation in the years 2012 and 2015. The 2012 data is analyzed in the context of the pp->wbb̄->lnbb̄ process where l = mu or e at sqrt(s) = 8 TeV and compared with simulations within the context of the Standard Model (SM). A cross section of sigma(pp->wbb̄->lnbb̄) = 0.64 +- 0.03 (stat) +- 0.10 (syst) +- 0.06 (theo) +- 0.02 (lumi) pb is measured, which is approximately one standard deviation higher than predictions. The data from 2015 is analyzed in the monophoton channel at sqrt(s) = 13 TeV both as a measurement of the cross section for pp->zg->nng and as a search for dark matter (DM). The SM cross section is measured as sigma(pp->zg->nng) = 66.5 +- 13.6 (stat) +- 14.3 +-(syst) +- 2.2 (lumi) fb which agrees with the NNLO SM prediction of 65.5 +- 3.3 fb. Limits are therefore set on the mass of vector or axial-vector mediator models of DM production up to 600 GeV for particle DM mass up to 10 GeV. An effective field theory model is also considered and values of the suppression scale of the coupling between DM and photons are excluded up to 540 GeV.
Download or read book A Measurement of Wbb Production and a Search for Monophoton Signals of Dark Matter Using the CMS Detector at the CERN LHC written by Thomas Mastrianni Perry and published by . This book was released on 2016 with total page 198 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents the results of two analyses of data from proton-proton collisions collected by the CMS Collaboration at the CERN LHC during operation in the years 2012 and 2015. The 2012 data is analyzed in the context of the pp->wbb̄->lnbb̄ process where l = mu or e at sqrt(s) = 8 TeV and compared with simulations within the context of the Standard Model (SM). A cross section of sigma( pp->wbb̄->lnbb̄ ) = 0.64 +- 0.03 (stat) +- 0.10 (syst) +- 0.06 (theo) +- 0.02 (lumi) pb is measured, which is approximately one standard deviation higher than predictions. The data from 2015 is analyzed in the monophoton channel at sqrt(s) = 13 TeV both as a measurement of the cross section for pp->zg->nng and as a search for dark matter (DM). The SM cross section is measured as sigma( pp->zg->nng ) = 66.5 +- 13.6 (stat) +- 14.3 +-(syst) +- 2.2 (lumi) fb which agrees with the NNLO SM prediction of 65.5 +- 3.3 fb. Limits are therefore set on the mass of vector or axial-vector mediator models of DM production up to 600 GeV for particle DM mass up to 10 GeV. An effective field theory model is also considered and values of the suppression scale of the coupling between DM and photons are excluded up to 540 GeV.
Download or read book Search for Dark Matter in Events with Missing Transverse Momentum and a Higgs Boson Decaying to Two Photons in Pp Collisions at S u221A written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Results of a search for new phenomena in events with large missing transverse momentum and a Higgs boson decaying to two photons are reported. Data from proton-proton collisions at a center-of-mass energy of 8 TeV and corresponding to an integrated luminosity of 20.3 fb-1 have been collected with the ATLAS detector at the LHC. The observed data are well described by the expected standard model backgrounds. Upper limits on the cross section of events with large missing transverse momentum and a Higgs boson candidate are also placed. Exclusion limits are presented for models of physics beyond the standard model featuring dark-matter candidates.
Download or read book Search for Dark Matter Produced in Association with a Leptonically Decaying Z Boson in Proton proton Collisions at s written by Albert M. Sirunyan and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Proceedings of the Fourth International Workshop on the Identification of Dark Matter written by Neil John Curwen Spooner and published by World Scientific. This book was released on 2003 with total page 684 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this workshop series is to assess the status of work attempting to identify what constitutes dark matter - in particular, to consider the techniques being used, how successful they are, and what new techniques are likely to improve prospects for identifying likely dark matter candidates in the future.
Download or read book A Search for an Excited Muon Decaying to a Muon and Two Jets in Pp Collisions at sqrt s written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this study, a new search signature for excited leptons is explored. Excited muons are sought in the channel ${pp}\to \mu {\mu }^{* }\to \mu \mu \ {\rm{jet}}\;{\rm{jet}}$, assuming both the production and decay occur via a contact interaction. The analysis is based on 20.3 fb-1 of pp collision data at a centre-of-mass energy of $\sqrt{s}\;=\;8\;{\rm{TeV}}$ taken with the ATLAS detector at the large hadron collider. No evidence of excited muons is found, and limits are set at the 95% confidence level on the cross section times branching ratio as a function of the excited-muon mass ${m}_{{\mu }^{* }}$. For ${m}_{{\mu }^{* }}$ between 1.3 and 3.0 TeV, the upper limit on $\sigma B({\mu }^{* }\to \mu q\bar{q}$) is between 0.6 and 1 fb. Limits on $\sigma B$ are converted to lower bounds on the compositeness scale [Lambda]. In the limiting case ${\rm{\Lambda }}={m}_{{\mu }^{* }}$, excited muons with a mass below 2.8 TeV are excluded. With the same model assumptions, these limits at larger ${\mu }^{* }$ masses improve upon previous limits from traditional searches based on the gauge-mediated decay ${\mu }^{* }\to \mu \gamma $.
Download or read book Search for Dark Matter Particles in Proton proton Collisions at sqrt s written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for dark matter particles directly produced in proton-proton collisions recorded by the CMS experiment at the LHC is presented. The data correspond to an integrated luminosity of 18.8 inverse femtobarns, at a center-of-mass energy of 8 TeV. The event selection requires at least two jets and no isolated leptons. The razor variables are used to quantify the transverse momentum balance in the jet momenta. The study is performed separately for events with and without jets originating from b quarks. The observed yields are consistent with the expected backgrounds and, depending on the nature of the production mechanism, dark matter production at the LHC is excluded at 90% confidence level for a mediator mass scale Lambda below 1 TeV. The use of razor variables yields results that complement those previously published.
Download or read book Search for Dark Matter and Supersymmetry with a Compressed Mass Spectrum in the Vector Boson Fusion Topology in Proton proton Collisions at Sqrt s written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A first search for pair production of dark matter candidates through vector boson fusion in proton-proton collisions at sqrt(s) = 8 TeV is performed with the CMS detector. The vector boson fusion topology enhances missing transverse momentum, providing a way to probe supersymmetry also in the case of a compressed mass spectrum. The data sample corresponds to an integrated luminosity of 18.5 inverse femtobarns recorded by the CMS experiment. The observed dijet mass spectrum is consistent with the standard model expectation. In an effective field theory, dark matter masses are explored as a function of contact interaction strength. The most stringent limit on bottom squark production with mass below 315 GeV is also reported, assuming a 5 GeV mass difference with respect to the lightest neutralino.
Download or read book Search for Dark Matter and Unparticles Produced in Association with a Z Boson in Proton proton Collisions at Sqrt s written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for evidence of particle dark matter (DM) and unparticle production at the LHC has been performed using events containing two charged leptons, consistent with the decay of a Z boson, and large missing transverse momentum. This study is based on data collected with the CMS detector corresponding to an integrated luminosity of 19.7 inverse femtobarns of pp collisions at the LHC at a center-of-mass energy of 8 TeV. No significant excess of events is observed above the number expected from the standard model contributions. The results are interpreted in terms of 90% confidence level limits on the DM-nucleon scattering cross section, as a function of the DM particle mass, for both spin-dependent and spin-independent scenarios. Limits are set on the effective cutoff scale Lambda, and on the annihilation rate for DM particles, assuming that their branching fraction to quarks is 100%. Additionally, the most stringent 95% confidence level limits to date on the unparticle model parameters are obtained.
Download or read book Search for Decays of Stopped Long lived Particles Produced in Proton proton Collisions at sqrt s written by and published by . This book was released on 2015 with total page 33 pages. Available in PDF, EPUB and Kindle. Book excerpt: A search has been performed for long-lived particles that could have come to rest within the CMS detector, using the time intervals between LHC beam crossings. The existence of such particles could be deduced from observation of their decays via energy deposits in the CMS calorimeter appearing at times that are well separated from any proton-proton collisions. Using a data set corresponding to an integrated luminosity of 18.6 fb-1 of 8 TeV proton-proton collisions, and a search interval corresponding to 281 h of trigger livetime, 10 events are observed, with a background prediction of 13.2+3.6 -2.5 events. Limits are presented at 95 % confidence level on gluino and top squark production, for over 13 orders of magnitude in the mean proper lifetime of the stopped particle. Assuming a cloud model of R-hadron interactions, a gluino with mass ≤1000 GeV and a top squark with mass ≤525 GeV are excluded, for lifetimes between 1 μs and 1000 s. Finally, these results are the most stringent constraints on stopped particles to date.
