Download or read book A Search for Dark Photons in the Photon Jet Final State with the CMS Detector at the LHC written by Dustin Ouray Kiefer Stolp and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: I present in this document an analysis searching for Dark Photons using the Compact Muon Solenoid detector at the Large Hadron Collider. The Dark Photon for this analysis is assumed to be low mass (m[subscript D]
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 Dark Matter with the ATLAS Detector written by Johanna Gramling and published by Springer. This book was released on 2018-08-01 with total page 290 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book discusses searches for Dark Matter at the CERN’s LHC, the world’s most powerful accelerator. It introduces the relevant theoretical framework and includes an in-depth discussion of the Effective Field Theory approach to Dark Matter production and its validity, as well as an overview of the formalism of Simplified Dark Matter models. Despite overwhelming astrophysical evidence for Dark Matter and numerous experimental efforts to detect it, the nature of Dark Matter still remains a mystery and has become one of the hottest research topics in fundamental physics. Two searches for Dark Matter are presented, performed on data collected with the ATLAS experiment. They analyze missing-energy final states with a jet or with top quarks. The analyses are explained in detail, and the outcomes and their interpretations are discussed, also in view of the precedent analysis of theoretical approaches. Given its depth of coverage, the book represents an excellent reference guide for all physicists interested in understanding the theoretical and experimental considerations relevant to Dark Matter searches at the LHC.
Download or read book Search for Dark Gauge Bosons Decaying Into Displaced Lepton Jets in Proton proton Collisions at 13 TeV with the ATLAS Detector written by Miriam Deborah Joy Diamond and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The dark photon ($A'$), the gauge boson carrier of a hypothetical new force, has been proposed in a wide range of Beyond the Standard Model (BSM) theories, and could serve as our window to an entire dark sector. A massive $A'$ could decay back to the Standard Model (SM) with a significant branching fraction, through kinetic mixing with the SM photon. If this $A'$ can be produced from decays of a dark scalar that mixes with the SM Higgs boson, collider searches involving leptonic final states provide promising discovery prospects with rich phenomenology. This work presents the results of a search for dark photons in the mass range $0.2 \lesssim m_{A'} \lesssim 10$ GeV decaying into collimated jets of light leptons and mesons, so-called ``lepton-jets". It employs 3.57 \fb of data from protonâ -proton collisions at a centre-of-mass energy of $\sqrt{s} =13$ TeV, collected during 2015 with the ATLAS detector at the LHC. No deviations from SM expectations are observed. Limits on benchmark models predicting Higgs boson decays to $A'$s are derived as a function of the $A'$ lifetime; limits are also established in the parameter space of $m_{A'}$ vs. kinetic mixing parameter $\epsilon$ . These extend the limits obtained in a similar search previously performed during Run 1 of the LHC, to include dark photon masses $2 \lesssim m_{A'} \lesssim 10$ GeV and to cover higher $\epsilon$ values for $0.2 \lesssim m_{A'} \lesssim 2$ GeV, and are complementary to various other ATLAS $A'$ searches. As data-taking continues at the LHC, the reach of lepton-jet analyses will continue to expand in model coverage and in parameter space.
Download or read book Searching for Long lived Dark Photons with the Heavy Photon Search Experiment written by Matthew Reagan Solt and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A heavy photon (also called a dark photon or A') is a hypothetical vector boson that arises from a massive U(1) abelian gauge symmetry. Heavy photons kinetically mix with the Standard Model photon, thus they are a natural portal to hidden sectors that are favored in a variety of dark sector scenarios, particularly for dark matter at the sub-GeV mass scale. The Heavy Photon Search Experiment (HPS) is a fixed target experiment at Jefferson Laboratory dedicated to searching for heavy photons in the MeV - GeV mass range and kinetic mixing strength ~1e-5 - 1e-10. It does so through two distinct searches - a search for a narrow mass resonance and, for sufficiently small couplings, a search for secondary vertices beyond a large prompt QED background. In order to perform such searches, the HPS utilizes a compact, forward acceptance spectrometer that must be able to reconstruct particle masses and vertices with extreme precision. Heavy photons are electro-produced from a continuous electron beam incident on a thin tungsten foil, and HPS is able to reconstruct the momentum of the subsequent decays to e+e- pairs using a silicon vertex tracker (SVT). HPS currently has three data sets - engineering runs in 2015 and 2016 as well as a physics run with an upgraded detector in 2019 - all at different beam energies and currents. Presented in this dissertation are heavy photon physics and motivations, introduction to the HPS detector and reconstruction, detector upgrades and other physics models of interest, and the results from the displaced vertex search from the HPS 2016 Engineering Run which was taken with a 2.3 GeV, 200 nA continuous electron beam and collected a total luminosity of 10753 1/nb (equivalent to 5.4 days of continuous beam). The 2016 Engineering Run displaced vertex search was performed in the mass range 60 - 150 MeV and in the range of kinetic mixing strength ~1e-10 - 1e-8, and the new results, which have a sensitivity to canonical A' production of ~0.4 events over a region of mass/coupling parameter space, exclude A' production above 6.05 times the canonical cross-section at a mass of 80.2 MeV and kinetic mixing strength of 2.12e-9. Even though HPS had insufficient data to set meaningful limits on the canonical A' production, this analysis demonstrated that the displaced vertex method is viable, backgrounds can be reduced to acceptable levels, and larger data sets can yield real exclusions or discovery. In fact, the background required to perform a displaced A' search (0.5 background events per mass search bin) was achieved in the unblinded 10% portion of the data set by implementing a new set of cuts. This significant background reduction stands as a considerable improvement over the previous analysis and approaches the sensitivity needed to observe the first A' candidates. After unblinding the entire data set, the remaining background events were studied and a search for decays which are further downstream and miss part of the acceptance of the tracker was performed. Finally, the sensitivity to another model which leads to displaced vertices is explored and preliminary projections show that HPS will have sensitivity to new territory with this data set. This combined work on the displaced vertex search is informative for future data sets that will search for A's in the same way but include simple, yet critical, upgrades to the detector. Studies of the detector upgrades are discussed and the expected sensitivity to future data sets with these upgrades is shown.
Download or read book The Physics of the Dark Photon written by Marco Fabbrichesi and published by Springer Nature. This book was released on 2020-11-23 with total page 85 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is about the dark photon which is a new gauge boson whose existence has been conjectured. Due to its interaction with the ordinary, visible photon, such a particle can be experimentally detected via specific signatures. In this book, the authors review the physics of the dark photon from the theoretical and experimental point of view. They discuss the difference between the massive and the massless case, highlighting how the two phenomena arise from the same vector portal between the dark and the visible sector. A review of the cosmological and astrophysical observations is provided, together with the connection to dark matter physics. Then, a perspective on current and future experimental limits on the parameters of the massless and massive dark photon is given, as well as the related bounds on milli-charged fermions. The book is intended for graduate students and young researchers who are embarking on dark photon research, and offers them a clear and up-to-date introduction to the subject.
Download or read book Searching for Dark Matter with the ATLAS Detector written by Steven Schramm and published by Springer. This book was released on 2018-07-07 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis describes the search for Dark Matter at the LHC in the mono-jet plus missing transverse momentum final state, using the full dataset recorded in 2012 by the ATLAS Experiment. It is the first time that the number of jets is not explicitly restricted to one or two, thus increasing the sensitivity to new signals. Instead, a balance between the most energetic jet and the missing transverse momentum is required, thus selecting mono-jet-like final states. Collider searches for Dark Matter have typically used signal models employing effective field theories (EFTs), even when comparing to results from direct and indirect detection experiments, where the difference in energy scale renders many such comparisons invalid. The thesis features the first robust and comprehensive treatment of the validity of EFTs in collider searches, and provides a means by which the different classifications of Dark Matter experiments can be compared on a sound and fair basis.
Download or read book Search for Dark Matter Produced in Association with a Higgs Boson Decaying to Two Bottom Quarks at ATLAS written by Yangyang Cheng and published by Springer. This book was released on 2016-09-29 with total page 183 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis reports on the search for dark matter in data taken with the ATLAS detector at CERN’s Large Hadron Collider (LHC). The identification of dark matter and the determination of its properties are among the highest priorities in elementary particle physics and cosmology. The most likely candidate, a weakly interacting massive particle, could be produced in the high energy proton-proton collisions at the LHC. The analysis presented here is unique in looking for dark matter produced together with a Higgs boson that decays into its dominant decay mode, a pair of b quarks. If dark matter were seen in this mode, we would learn directly about the production mechanism because of the presence of the Higgs boson. This thesis develops the search technique and presents the most stringent production limit to date.
Download or read book A Measurement of Z small Nu small N small Gamma Production and a Search for New Physics in Monophoton Events Using the CMS Detector at the LHC written by James Joseph Buchanan and published by . This book was released on 2019 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents several studies of monophoton final states using 35.9 fb^-1 of 13 TeV proton-proton collision data collected by the CMS experiment at the LHC in 2016. The standard model Z([small nu] [small n̄ū])[small gamma] cross section is measured as a function of photon transverse momentum. No significant deviations from standard model predictions are observed. The results are also interpreted in the context of several new physics models. Limits are placed on new particle masses in simplified models of dark matter, the suppression scale of a dark matter effective field theory model, and the graviton mass scale in a model of extra spatial dimensions.
Download or read book Characterization of Jets in Heavy Ion Collisions Using Photons at the LHC with the CMS Detector written by Richard Alexander Barbieri and published by . This book was released on 2017 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: Using the CMS detector at the LHC, a quantitative study of jet energy loss and angular deflection inside the high energy-density medium formed in PbPb collisions is made. Photons are used to measure the initial state of a color-charged probe while jet reconstruction is used to measure the final state. Significant loss of energy to the medium as a function of initial parton momentum is observed, while no significant angular deflection is found.
Download or read book New Angular Search for Exotic Physics in the Photon jet Final State Using the ATLAS Detector on the LHC written by Robert Keyes and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "This thesis outlines developments towards a new analysis and search technique for heavy resonances in angular distributions of photon+jet final states for the 2012 data set from the ATLAS detector on the LHC. In particular, a new angular variable tailored to the photon+jet channel was defined which distinguishes between background and expected signals, the corresponding angular observable sensitivity was optimized using ATLAS excited quark samples and JetPhox MC samples, and an optimal mass binning scheme was derived from the measured mass resolution. Ongoing work is being done to publish the analysis." --
Download or read book From the Fermi Scale to Cosmology written by Alberto Salvio and published by Frontiers Media SA. This book was released on 2019-12-06 with total page 265 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Search for Dark Matter in the Monophoton Final State at CMS written by Alexandra Carley Kopecky and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The final state of a photon ([gamma]) and missing transverse energy in pp collisions can be used as a valuable test of the Standard Model. The Standard Model production of Z(vv̄) + [gamma] is a precise process with no dependence on tuned parameters, so it is sensitive to contributions from new physics events. At the same time, this constitutes an irreducible background for new physics searches with the same final state. This dissertation discusses a measurement of associated Z[gamma] production, where Z decays into neutrinos. The data are collected in pp collisions at [square root s] = 7 TeV by the CMS experiment and correspond to an integrated luminosity of 5.0 fb−1. Descriptions are provided for the methods of reducing and estimating the sources of background. A total number of 73 events are observed, which agrees well with the Standard Model expectation of 75.1 ± 9.5 events. These results are interpreted in terms of a search for dark matter, which is widely accepted as the nonbaryonic dominant contribution to the matter density of the Universe. Models of production of dark-matter particles (x) are used to set 90% confidence level upper limits of 13.6 - 15.4 fb on x production in the [gamma+ missing transverse energy] final state. At the time of publication, these provided the most sensitive upper limits for spin-dependent x-nucleon scattering for x masses (M[subscript x]) between 1 and 100 GeV. For spin-dependent contributions, the present limits are extended to M[subscript x]
Download or read book Search for Dark Matter and Supersymmetry in the Single Photon Events with the ATLAS Detector written by Mengqing Wu and published by . This book was released on 2015 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents the search for new physics in the final state containing a single photon and missing transverse momentum. The analysis is performed on 20.3fb-1 of proton-proton collisions data at a center-of-mass energy of 8 TeV collected by the ATLAS detector at the Large Hadron Collider. Given the good agreement of the data with the Standard Model pre- diction of such events, an upper limit to the visible cross section produced by new physics is derived. The observed limit at 95% confidence level is 3.64 fb.In this thesis, the results are also interpreted as limits in the parameter space of two new physics models. The first model is an effective field theory, inspired by Fermi-LAT results, in which dark matter particles couple to photons via a contact interaction vertex. Limits are set on the effective mass scale and depend on the postulated coupling constants. The limits set in this dark matter model provide an effective constraint in the parameter space of the theory compatible with the Fermi-LAT results. The second one is a simplified supersymmetric model describing squark pair production with their subsequent decay into a quark and a neutralino. The photon is emitted as initial or final state radiation and the spectrum is compressed, i.e. the mass difference between the squark and the neutralino is assumed to be small. Limits are set on the production cross-section; squark masses are excluded up to 250 GeV in the very compressed region. As the photon can be irradiated from the intermediate squark, this final state would eventually provide the possibility to probe the charge of the squark.A preliminary study has also been carried out to show the search sensitivity with 13 TeV data, which indicate that the limits presented in this thesis can already be improved by 10% with 5fb-1.
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.
