Download or read book Search for Dark Photons from Neutral Meson Decays in P p and D Au Collisions at SNN written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The standard model (SM) of particle physics is spectacularly successful, yet the measured value of the muon anomalous magnetic moment (g-2)? deviates from SM calculations by 3.6?. Several theoretical models attribute this to the existence of a ?dark photon,? an additional U(1) gauge boson, which is weakly coupled to ordinary photons. For this study, the PHENIX experiment at the Relativistic Heavy Ion Collider has searched for a dark photon, U, in ?0,?????????e+e- decays and obtained upper limits of ?(2×10-6) on U-? mixing at 90% C.L. for the mass range 30msubU/sub90 MeV/csup2/sup. Lastly, combined with other experimental limits, the remaining region in the U-? mixing parameter space that can explain the (g-2)sub?/sub deviation from its SM value is nearly completely excluded at the 90% confidence level, with only a small region of 29msubU

Download or read book Search for Dark Photons from Neutral Meson Decays in math mi p mi mo mo mi p mi math and math mi d mi mo mo mi Mathvariant written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The standard model (SM) of particle physics is spectacularly successful, yet the measured value of the muon anomalous magnetic moment (g-2)[mu] deviates from SM calculations by 3.6[sigma]. Several theoretical models attribute this to the existence of a "dark photon," an additional U(1) gauge boson, which is weakly coupled to ordinary photons. For this study, the PHENIX experiment at the Relativistic Heavy Ion Collider has searched for a dark photon, U, in [pi]0, [eta]2!gamma]e+e- decays and obtained upper limits of [theta](2×10-6) on U-[gamma] mixing at 90% C.L. for the mass range 30

Download or read book Search for the Dark Photon in pi 0 Decays written by and published by . This book was released on 2015 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: A sample of 1.69 × 107 fully reconstructed [pi]0 2![gamma]e+e- decay candidates collected by the NA48/2 experiment at CERN in 2003-2004 is analyzed to search for the dark photon (A') production in the [pi]02!gamma]A' decay followed by the prompt A' 2!e+e- decay. No signal is observed, and an exclusion region in the plane of the dark photon mass mA' and mixing parameter [epsilon]2 is established. The obtained upper limits on [epsilon]2 are more stringent than the previous limits in the mass range 9 MeV/c2

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 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 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 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 a Dark Photon in the Hps Experiment written by Sebouh Paul and published by . This book was released on 2018 with total page 197 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Heavy Photon Search (HPS) experiment at Jefferson Lab is designed to search for a hypothesized elementary particle called a dark (heavy) photon. Such a particle would behave as a mediator between dark matter and the Standard Model through a kinetic mixing with the Standard Model’s photon. The search is performed by scattering GeV-scale electrons off tungsten nuclei in a fixed target and looking for a resonance and/or displaced vertices amidst a background of radiative QED trident events. These background events are kinematically identical to the events in which dark photons are produced and decay into lepton pairs. Several other types of reactions take place in this experiment, such as Bethe-Heitler tridents, Moeller scattering, wide-angle bremsstrahlung and elastic scattering off the nucleus. Each of these types of background reactions are used for calibration of the detector. For one of these calibration studies, we have measured the form factors for electrons scattering elastically and nearly-elastically off a carbon target and compared these to predicted values. A resonance search, performed on 10% of the dataset taken in 2016 with a 2.306 GeV beam, shows no sign of a dark photon in the mass range 45-200 MeV. Preliminary upper limits on the square of the dark-photon’s kinetic coupling to the Standard Model photon have been set in the 10−6 − 10−5 range at 95% confidence for every mass hypothesis in this mass range.

Download or read book Search for Heavy Long lived Particles that Decay to Photons in p bar p Collisions at sqrt s written by and published by . This book was released on 2007 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation presents the results of the first search for heavy, neutral, longlived particles that decay to photons at a hadron collider. We use a sample of +jet+missing transverse energy events in $p \bar{p}$ collisions at √s = 1.96 TeV taken with the Collider Detector at Fermilab. Candidate events are selected based on the arrival time of a high-energy photon at the electromagnetic calorimeter as measured with a timing system that was recently installed. The final result is that we find 2 events, using 570±34 pb-1 of data collected during 2004-2005 at the Fermilab Tevatron, consistent with the background estimate of 1.3±0.7 events. While our search strategy does not rely on model-specific dynamics, we interpret this result in terms of cross section limits in a supersymmetric model with $\vec{X}$$0\atop{1}$ eG and set a world-best e 01 mass reach of 101 GeV/c2 at e = 5 ns. We can exclude any [gamma]+jet+missing transverse energy signal that would produce more than 5.5 events.

Download or read book Search for Heavy Long lived Particles that Decay to Photons in Ppbar Collisions at Sqrt s written by Peter Wagner and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation presents the results of the first search for heavy, neutral, longlived particles that decay to photons at a hadron collider. We use a sample of +jet+missing transverse energy events in pp̄ collisions at s = 1.96 TEV taken with the Collider Detector at Fermilab. Candidate events are selected based on the arrival time of a high-energy photon at the electromagnetic calorimeter as measured with a timing system that was recently installed. The final result is that we find 2 events, using 570"34 pb−1 of data collected during 2004-2005 at the Fermilab Tevatron, consistent with the background estimate of 1.3"0.7 events.

Download or read book Search for Decays of the Z A0 Into a Photon and a Pseudoscalar Meson written by ALEPH. and published by . This book was released on 1990 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Search for Dark Photons from Supersymmetric Hidden Valleys written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Photon and Neutral Pi 0 Production in 197 Au 197 Au Collisions at Sqrt S NN written by and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Inclusive transverse momentum spectra of photons and[pi][sup 0]s at mid-rapidity are studied as a function of collision centrality for[sup 197]Au+[sup 197]Au collisions at[radical]s[sub NN]= 130 GeV. Photon pair conversions have been reconstructed from charged tracks measured by the main Time Project Chamber of the STAR experiment at the RHIC heavy ion facility. The transverse momentum resolution of photons with this method is estimated to be[Delta]p[sub t]/p[sub t]= 2% at 0.125 GeV/c and 5% at 2.5 GeV/c. Photon spectra were measured up to a transverse momentum of 2.4 GeV/c between[+-] 0.5 units of rapidity. The dominant photon production mechanism, the[pi][sup 0][yields][gamma][gamma] decay, was measured between 0.25-2.5 GeV/c and[+-] 1 units of rapidity. Spectra are reported for the top 11%, 11-34% and 34-85% centrality classes. It was observed that in mid-central and central collisions the relative contribution of the[pi][sup 0][yields][gamma][gamma] decay to the inclusive photon spectrum decreases above a transverse momentum of 1.65 GeV/c. In central collisions the magnitude of the decrease from p[sub t]= 1.65 GeV/c to 2.4 GeV/c is 20%. It is unlikely that contributions from other[pi][sup 0] decay channels and other particle decays fully explain this decrease. The centrality dependence on the shapes of the[pi][sup 0] spectra was analyzed with Boltmann and Bose-Einstein functions. In the transverse momentum windows of the spectra, the extracted temperatures are near 0.295 GeV. These temperatures are substantially higher than those extracted from[pi][sup[+-]] spectra in a lower range of transverse momentum. This is an indication that the shapes of the pion spectra deviate from purely exponential shapes.

Download or read book Search for Heavy Long Lived Neutralinos that Decay to Photons at CDF II Using Photon Timing written by and published by . This book was released on 2008 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors present the results of the first hadron collider search for heavy, long-lived neutralinos that decay via {tilde {chi}}1° → [gamma]{tilde G} in gauge-mediated supersymmetry breaking models. Using an integrated luminosity of 570 ± 34 pb−1 of p{bar p} collisions at √s = 1.96 TeV, they select [gamma]+jet+missing transverse energy candidate events based on the arrival time of a high-energy photon at the electromagnetic calorimeter as measured with a timing system that was recently installed on the CDF II detector. They find 2 events, consistent with the background estimate of 1.3 ± 0.7 events. While the search strategy does not rely on model-specific dynamics, they set cross section limits and place the world-best 95% C.L. lower limit on the {tilde {chi}}1° mass of 101 GeV/c2 at [tau]{sub {tilde {chi}}1°} = 5 ns.

Download or read book A Search for Light Photino in Neutral Pion Decay written by M. I. Dobroliubov and published by . This book was released on 1987 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Measurement of Neutral Mesons and Direct Photons in Pp Collisions with ALICE written by Daniel Mühlheim and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Measurement of Neutral Mesons and Direct Photons in Pb Pb Collisions at sNN written by Lucia Leardini and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: