High Energy Physics Seminars

High Energy
Wednesday, September 29, 2021
4:00 PM
Physics Building, Room 204

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"TBA"


Amy L. Connolly
[Host: Craig Dukes]
ABSTRACT:

TBA

High Energy
Wednesday, September 1, 2021
4:00 PM
Physics Building, Room 204

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"TBA"


Dr. Andres Delannoy , University of Tennessee
[Host: Chris Neu]
ABSTRACT:

TBA

Joint Nuclear/HEP seminar

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Meeting ID: 922 8790 9487
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Wednesday, April 28, 2021
4:00 PM
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"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. 

VIDEO:
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Wednesday, April 21, 2021
4:00 PM
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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
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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.

VIDEO:
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Wednesday, March 24, 2021
4:00 PM
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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.

VIDEO:
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Wednesday, March 17, 2021
4:00 PM
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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.

VIDEO:
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Wednesday, March 3, 2021
4:00 PM
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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
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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
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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.

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