# High Energy Physics Seminars

Joint Nuclear/HEP seminar

##### Meeting ID: 922 8790 9487Password: HEPseminar

Wednesday, April 28, 2021
4:00 PM
Online, Room via Zoom
Note special room.

## "First results from the Fermilab Muon g-2 experiment"

Manolis Kargiantoulakis , Fermilab
[Host: Craig Group and Dinko Pocanic]
ABSTRACT:

The Muon g − 2 Experiment at Fermilab has measured the anomalous magnetic moment of the muon to 460 parts-per-billion, based on data collected during the first physics run in 2018. The experiment determines the anomalous precession frequency of the muon spin inside the highly uniform and precisely measured magnetic field of our storage ring. Our result is in excellent consistency with (and slightly more precise than) the BNL measurement of the same quantity from two decades ago. The combination of the experimental measurements increases the tension with the Standard Model prediction, enhancing the significance of the discrepancy to 4.2σ. In this seminar we will present the challenging experimental measurement and discuss the status of the discrepancy.

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Wednesday, April 21, 2021
4:00 PM
Online, Room via Zoom
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## "Is double gluon bremsstrahlung in a quark-gluon plasma accurately described by the Ncolor = ∞ approximation to QCD?"

Omar Elgedawy , University of Virginia - Department of Physics
[Host: Peter Arnold]
ABSTRACT:
QCD jets produced from colliding two heavy nuclei play an important role in understanding properties of the Quark Gluon Plasma produced in these energetic collisions. During their travel through the medium, high energy partons lose their energy due to interactions with the medium through elastic collisions and medium-induced splitting processes like bremsstrahlung and pair production. In the high energy limit, these splitting processes are coherent over large distances and can no longer be treated as quantum mechanically independent, leading to a suppression of the splitting rate known as the Landau-Pomeranchuk-Migdal effect. An important question that arises is whether consecutive splittings of the high energy particle overlap within the formation time of an individual splitting. This case has been analyzed in the Nc = ∞ limit within the thick medium approximation. To see if this result applies for real QCD with Nc = 3, we calculate the next to leading order correction (i.e. O(1/N2)) to the gluon double-splitting. We have already completed a subset of the diagrams known as sequential diagrams. In this talk, I will report first results on whether the Nc = ∞  approximation to the differential rate of overlapping double bremsstrahlung of gluons is reliable, and in particular whether the correction is large or small compared to the naive expectation of 1/N2c ∼10% for Nc = 3.

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Wednesday, March 31, 2021
4:00 PM
Online, Room viz Zoom
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## "Probing modified gravitational-wave propagation through tidal measurements of binary neutron star mergers"

Nan Jiang , University of Virginia - Department of Physics
[Host: Kent Yagi]
ABSTRACT:

Gravitational-wave sources can serve as standard sirens to probe cosmology by measuring their luminosity distance and redshift.  Such standard sirens are also useful to probe theories beyond General Relativity with a modified gravitational-wave propagation.  Most previous studies on the latter assume multi-messenger observations so that the luminosity distance can be measured with gravitational waves while the redshift is obtained by identifying sources’ host galaxies from electromagnetic counterparts.  Given that gravitational-wave events of binary neutron star coalescences with associated electromagnetic counterpart detections are expected to be rather rare,  it is important to examine the possibility of using standard sirens to probe gravity with gravitational-wave measurements alone.  In this paper, we achieve this by extracting the redshift from the tidal measurement of binary neutron stars (that was originally proposed within the context of gravitational-wave cosmology).  We also improve previous work by considering multi-band gravitational-wave observations between ground-based (e.g.  Einstein Telescope) and space-based (e.g.  DECIGO) interferometers. We find that such multi-band observations with the tidal information can constrain a parametric non-Einsteinian deviation in the luminosity distance more stringently than the case with electromagnetic counterparts (due to a larger number of available events) by a factor of a few.  We also map the above-projected constraints on the parametric deviation to those on specific theories beyond General Relativity.

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Wednesday, March 24, 2021
4:00 PM
Online, Room via Zoom
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## "Search for Long-Lived Particles at CMS in Runs 2 and 3 and beyond"

Ang Li , University of Virginia - Department of Physics
[Host: Chris Neu]
ABSTRACT:

Many physics beyond standard model predicts the existence of long-lived particles, which will travel a relatively long distance in the detector after it’s generation and leave some special signals in the detector such as displaced vertices, displaced jets and delayed leptons etc.. This talk introduces the search for displaced vertex, including event selection, vertex reconstruction and data-driven background estimation method. In the meanwhile, the talk also includes the structure and mechanics study for MIP Timing Detector, which is capable to measure the time information precisely when a charged particle pass through it and will be installed in CMS for high luminosity LHC era.

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Wednesday, March 17, 2021
4:00 PM
Online, Room via Zoom
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## "Recent Results at the NOvA Neutrino Oscillation Experiment and Developments for Future Sensitivity Improvements"

Andrew Sutton , University of Virginia - Department of Physics
[Host: Craig Group]
ABSTRACT:

NOvA is a long-baseline accelerator neutrino experiment that can probe outstanding questions in neutrino oscillation physics. Among these are: the neutrino mass hierarchy, CP violation in the lepton sector, and the determination of the neutrino mixing angle θ23. NOvA has access to these parameters by observing electron neutrino appearance and muon neutrino disappearance over an 810 km baseline. For the high statistics muon neutrino measurements the shape of the energy spectra can be used to further constrain the oscillation parameters owing to the energy dependence of neutrino oscillations. Therefore, a high resolution measurement of the neutrino energy is necessary to make precision measurements of those parameters. Moreover, uncertainties on detector calibration and neutrino interaction models have a significant impact on measurement sensitivity. NOvA has an ongoing test beam effort to improve understanding of the detector response and reduce energy calibration uncertainties. Additionally, a Long Short-Term Memory (LSTM) neural network has been developed to estimate muon neutrino and provides improved energy resolution. Interaction model uncertainties can be further addressed by adversarial network training which can be employed with different interaction generators to increase the robustness and performance of the LSTM energy estimator against model variations. This talk will present the most recent NOvA oscillation results and show ongoing work to reduce systematic uncertainties and further improve measurement sensitivity.

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Wednesday, March 3, 2021
4:00 PM
Online, Room via Zoom
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## "Mu2e: A New Charged Lepton Flavor Violation Experiment: Muon-Electron Conversion at Sensitivity < 10-16"

Robert Bernstein , Fermi National Lab
[Host: Craig Group]
ABSTRACT:

The Mu2e experiment will measure the charged-lepton flavor violating (CLFV) neutrino-less conversion of a negative muon into an electron in the field of a nucleus. The conversion process results in a monochromatic electron with an energy slightly below the muon rest mass. Mu2e will improve the previous measurement by four orders of magnitude using a new technique, reaching a SES (single event sensitivity) of 3 x 10^{-17} on the conversion rate, and a discovery at 2 x 10^{-16}. The experiment will reach mass scales of nearly 10^4 TeV, far beyond the direct reach of colliders. The experiment is sensitive to a wide range of new physics, complementing and extending other CLFV searches.

Mu2e is under design and construction at the Muon Campus of Fermilab with our first physics run in early 2025.

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Wednesday, February 3, 2021
4:00 PM
Online, Room via Zoom
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## "Reaching for the stars with CNO solar neutrinos"

Zara Bagdasarian , UC, Berkeley
[Host: Craig Dukes]
ABSTRACT:

The prime energy producer in the sun is the fusion of hydrogen to form helium. However, there is more than one way for this fusion to takeplace: for stars the size of the sun or smaller, the proton-proton (pp) chain reactions dominate (~99%), while in heavier stars, the carbon-nitrogen-oxygen (CNO) cycle is expected to play a more important role. Not only these fusion reactions would not have been possible without the emission of neutrinos, neutrinos are the only way to directly access the processes in the core of the sun.

Borexino experiment, located at the Laboratori Nazionali del Gran Sasso, was built with a primary goal of the Be7 solar neutrinos (part of pp chain) detection. In more than a decade of data taking, Borexino has not only demonstrated the unprecedentedly high sensitivity towards Be7 solar neutrinos (<3%) but performed a comprehensive study of low-energy neutrinos from the complete pp-chain. After a number of developments in both hardware and software, Borexino has presented the first experimental evidence of the up-to-now elusive CNO fusion cycle in the Sun. The absence of the CNO neutrinos signal is disfavoured by the Borexino experiment at 5σ.

VIDEO:
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Wednesday, January 20, 2021
4:00 PM
Online, Room via Zoom
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## "Search for resonant decays to neutral Standard Models Bosons and MET with the CMS Detector, and the CMS Hadron Calorimeter Upgrade"

Grace Cummings , University of Virginia - Department of Physics
[Host: Bob Hirosky]
ABSTRACT:

Direct decays of proposed heavy force mediator particles to standard model leptons
have been largely excluded by past LHC searches, challenging theorists to explore more complex
decay chains. We begin our search with a framework model of a Leptophobic Z' cascading to a
pair anomalons, new Beyond the Standard Model fermions. These heavy intermediate particles decay in turn to neutral standard model bosons and a stable anomalon, which appears in the Compact Muon Solenoid (CMS) detector as missing transverse momentum (pT-miss). From a model independent point of view, this topology creates an interesting structure with a resonantly produced particle cascading to a final state with 2 missing particles, with each level of the cascade including new particles with unknown masses. To turn this into a bump hunt for the resonant particle, we employ Recursive Jigsaw Reconstruction (RJR), a rule-based methodology to systematically reduce degrees of freedom, allowing for the calculation of mass estimators at each level of our decay chain. RJR is an example of how analysis tools are evolving to be sensitive to the most well-hidden of new physics, and the detectors are doing the same. I will also give an overview of the Phase I upgrade to the CMS Hadronic Calorimeter.

VIDEO:
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Wednesday, January 6, 2021
4:00 PM
Online, Room via Zoom
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## "Low-Mass Dijet Resonance Search with Calo-Scouting Techniques using CMS Run-II Data at sqrt(s)=13 TeV and, the Studies on Improvements of the CMS Detector "

Ali Eren Simsek , Cukurova University
[Host: Chris Neu]
ABSTRACT:

Physics models that allow the Standard Model to spread over a larger area often require new particles that attached to quarks and gluons and decay to dijets. The natural width of the resonances in the dijet mass spectrum (mjj) increases with coupling, and may vary from narrow resonance to wide resonance compared to experimental resolution. For example, in a model where DM (Dark Matter) particles are attached to quarks through a "DM Mediator" and the mediator can be decay to a pair of DM particles or a pair of jets and therefore can be observed as a dijet resonance. In this seminar, searches are presented for resonances with mass between 0.6 and 1.8 TeV decaying to dijet final states in proton-proton collisions at sqrt(s)=13 TeV.  The searches are performed with dijets that are reconstructed from calorimeter information in the trigger using data corresponding to an integrated luminosity of 122 /fb. The dijet mass spectrum is compared to a smooth parameterization of the QCD background and simulations of resonance signals decaying into parton pairs. Upper limits at 95% CL are presented on the production cross section of narrow quark-quark, quark-gluon and gluon-gluon resonances. This seminar also includes the studies on minor and major CMS upgrades such as HGCAL (High-Granularity Calorimeter) MIP (Minimum Ionizing Particle) Calibration Analysis with test-beam data and full ~607 meters of SPS (Super Proton Synchrotron) H2 Beamline simulation using Geant4 Beamline for 2018 HGCAL test-beam.

VIDEO:
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Wednesday, December 2, 2020
4:00 PM
Physics Building, Room 204

## "New physics searches in ATLAS"

Boping Chen , Iowa State University
[Host: Chris Neu]
ABSTRACT:

Standard Model(SM) is a very successful theory in particle physics, which can explain most of the high energy experiment. However, still there are many open questions for the SM, such as dark matter, dark energy and gravity interaction. One of the main goal for both ATLAS and CMS detector in LHC is to search for the new physics beyond the Standard model, to give us some hint for those open questions. This talk presents two analyses for the new physics search: 1: Search for the heavy resonance Z' decaying into a Higgs boson and a photon; 2: Search for lepton flavor violation Z->emu decay. Both of these two analyses use proton proton collision data set collected by ATLAS detector from 2015 to 2018. This talk also covers some upgrade study for the ATLAS inner tracker.

VIDEO:
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Monday, November 23, 2020
4:00 PM
Online, Room via Zoom
Note special date.
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## "Determination of the Jet Energy Scale Corrections for the Low pT Jets at root(s) = 13 TeV in CMS and Activities at HCAL Phase-1 Upgrade"

Zuhal Seyma Demiroglu , Cukurova University
[Host: Chris Neu]
ABSTRACT:

The most abundant objects produced in high-energy proton-proton collisions at the LHC are jets which are reconstructed from topologically associated energy depositions in calorimeter cells, charged-particle tracks, or simulated particles. Ideally, jets are corrected due to the intrinsic limitations of the detector system. In CMS, reconstructed jets are calibrated by using a factorized approach. This seminar will present two analyses related to jet energy scale corrections focus on the low pT region. The first part of the talk is dedicated to the Monte Carlo (MC) truth jet energy corrections for no pileup QCD PYTHIA8 sample. The study is performed using the anti-kT clustering algorithm with a distance parameter R = 0.4 in the pseudorapidity range |η| < 5.191 for jet transverse momentum 10 < pT < 905 GeV. The second part presents the calibration of the jet energy scale with respect to residual differences between data and simulation after simulation-based pre-calibrations are applied. In this analysis, low pile-up data collected by the CMS experiment in 2015 at a center-of-mass energy of 13 TeV are used. The correction factors depending on jet pT and η are derived by using two different methods based on the dijet final states in the region of |η| < 5.191 pseudorapidity and 20 < pT < 114 GeV. This will make an important contribution to the physics analysis to be performed using the low pT jets. In addition, previous physics analysis, and activities at the Phase-1 Upgrade of the CMS Hadron Calorimeter will be also presented.

VIDEO:
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Wednesday, November 18, 2020
4:00 PM
Online, Room via Zoom
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## "Measurement of the cross section of top quark pairs in association with a photon in lepton + jets events at root(s) = 13 TeV with CMS full Run II data"

Nabin Poudyal , Wayne State University
[Host: Chris Neu]
ABSTRACT:

The production cross-section of top quark pairs in association with a photon is measured in lepton + jets final state events during proton-proton collisions at LHC 13TeV energy using the full Run II data collected by CMS with the total integrated luminosity of  137 fb-1. The study of top quark pair production in association with a photon provides us with important information on top quark electroweak coupling. It is also sensitive to beyond the Standard Model. The analysis is done in a semi leptonic decay channel with a well isolated high Pt lepton, at least four jets from the hadronization of quarks, and an isolated photon. The photons may be emitted from initial state radiation, top quarks, and decay products of top quarks. The simultaneous maximum likelihood fitting of several control regions and kinematic observables is done extensively and carefully to distinguish the ttγ signal process from various backgrounds. The inclusive cross section of ttγ process is measured for a photon with the transverse momentum Pt ≥ 20 GeV.

VIDEO:
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Wednesday, November 11, 2020
4:00 PM
Online, Room via Zoom
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## "Search for Displaced Leptons & Beam Tests for the CMS Pixel Detector Upgrade"

Bryan Cardwell , Ohio State University
[Host: Chris Neu]
ABSTRACT:

I present the two foci of my graduate research: a search for long-lived beyond-the-Standard-Model particles and R&D for the high-luminosity upgrade of the CMS pixel detector. First, I discuss the search for long-lived particles, which is performed in over 100 fb-1 of 13 TeV proton-proton collision data collected by the CMS experiment and uses electron and muon transverse impact parameter to identify displaced leptons, an exotic signature that is not covered by traditional analyses. In the second portion of the talk, I discuss the upcoming CMS silicon pixel detector upgrade, which will result in significant improvements in both functionality and radiation tolerance to stand up to the unprecedented particle flux and radiation dose of the High-Luminosity LHC. The discussion will focus on beam tests of prototype sensors and readout chips performed at the Fermilab Test Beam Facility.

VIDEO:
Special HEP seminar

##### https://us02web.zoom.us/j/81175477993?pwd=MWlvQVI4NlE4d2FBQjNrdEpsZHJRUT09

Thursday, November 5, 2020
4:00 PM
Online, Room via Zoom
Note special date.
Note special room.

## "Gravitational wave memory effects in Brans-Dicke theory"

Shammi Tahura , University of Virginia - Department of Physics
[Host: Kent Yagi]
ABSTRACT:

When gravitational waves pass through observers located far away from the source, they cause oscillatory distortions of the separations among the observers. There is one more interesting phenomenon that the gravitational waves can create lasting relative displacements of the observers, which is called the gravitational wave memory effect. Such effects are closely related to infrared properties of gravity and other massless field theories, including their asymptotic symmetries and conserved quantities. In this talk, I will present the Brans-Dicke theory in Bondi-Sachs form, discussing asymptotic symmetries, conserved charges, and the gravitational wave memory effects.

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Wednesday, November 4, 2020
3:30 PM
Online, Room via Zoom
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## "Latest Oscillation Results Combining Neutrino and Antineutrino Data from the NOvA Experiment"

Michael Baird , University of Virginia - Department of Physics
[Host: Craig Dukes]
ABSTRACT:

The NOvA experiment is a long-baseline neutrino oscillation experiment that uses the NuMI beam from Fermilab to detect both electron and muon flavored neutrinos in a Near Detector, located at Fermilab, and a Far Detector, located at Ash River, Minnesota. NOvA’s primary physics goals include precision measurements of neutrino oscillation parameters, such as θ23 and the atmospheric mass- squared splitting, along with probes of the mass hierarchy and the CP violating phase. This talk will present the latest NOvA results using a combined neutrino and anti-neutrino dataset based on a beam exposure of approximately 13 × 1020 protons-on-target in each dataset.

VIDEO:
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Wednesday, October 28, 2020
4:00 PM
Online, Room via Zoom
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## "Heavy or dark photon searches at Jefferson Lab"

Stepan Stepanyan , JLAB
[Host: Craig Dukes]
ABSTRACT:
The overwhelming evidence for dark matter (DM) in cosmological observations, manifested by its gravitational interactions, has inspired a major experimental effort to uncover its particle nature. The LHC, as well as direct and indirect detection experiments, have significantly constrained one of the best-motivated weak-scale DM models (WIMPs as dark matter candidates). In contrast, scenarios involving a light hidden sector dark matter with mediators in the MeV-GeV range has garnered a good deal of attention. Models with a hidden U(1) gauge symmetry, with a "dark" or "hidden sector" photons, are particularly attractive as they can be tested experimentally. If they exist, dark or heavy photons mix with ordinary photons through kinetic mixing, which induces their weak coupling to electrons, ∈e. Since they couple to electrons, heavy photons are radiated in electron scattering and can subsequently decay into e+e-. Experiments at Jefferson Lab use these features to search for heavy photons in the mass range of 20 MeV/c2 to 500 MeV/c2 and couplings of ∈2 > 10 -10 .
In this talk, I will summarize the experimental program for dark photon searches at Jefferson Lab. Results from the experiments that already took data, APEX and HPS, will be discussed together with plans for future measurements.

VIDEO:
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Wednesday, October 14, 2020
4:00 PM
via Zoom, Room Online
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## "Digital archaeology: Tomographic Imaging of the Great Pyramid of Giza"

Alan Bross , Fermilab
[Host: Craig Dukes]
ABSTRACT:

In 1970 L.  Alvarez et al. reported on the first experiment to use cosmic-ray muons to investigate the interior of a very large structure. That structure was Khafre's Pyramid at Giza.  In 2017, the Scan Pyramids team reported on the discovery of a new large void in the Great Pyramid (Khufu).  Although they used modern equipment, their system was not much larger than the one used by Alvarez's team. In order for the technique of cosmic-ray muon tomography to be able to answer detailed questions regarding the core structure of these enormous creations, a new approach must be taken.  The Exploring the Great Pyramid (EGP) Mission will use detector technology currently deployed in high-energy physics experiments to field very large muon telescopes outside of the Great Pyramid.  This will allow for a high-resolution study of almost all of its internal structure. It will go beyond simply looking for voids, but will potentially yield new information on the building techniques used to construct the Great Pyramid.  In this talk, I will review previous experiments, describe in detail the techniques the EGP Mission proposes to use and present preliminary simulation results.

VIDEO:
High Energy
Wednesday, March 4, 2020
4:00 PM
Physics Building, Room 204