High Energy Physics Seminars History

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

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ABSTRACT:

The Muon-to-Electron-Conversion (Mu2e) Experiment is a high-precision, intensity-frontier experiment being developed at Fermilab which will search for coherent, neutrino-less muon to electron conversion in the presence of an atomic nucleus. Such a process would exhibit charged lepton flavor violation (CLFV), which has not yet been observed. Continuing the search for CLFV, Mu2e will improve the sensitivity by four orders of magnitude over the present limits. In the search for beyond the standard model (BSM) physics, Mu2e is uniquely sensitive to a wide range of models by indirectly probing mass scales up to the energy scale of 104 TeV. While muon-to-electron-conversion is permissible through neutrino oscillations in an extension of the standard model, the rate is extremely low at about one event in 1054. By design, the background for the experiment will be well-understood and kept at a sub-event level, which results in the observation of muon-to-electron conversion as direct confirmation of BSM physics. The largest background comes from processes initiated by cosmic-ray muons, which will produce approximately one CLFV-like event per day. In order to reduce this rate to less than one event over the lifetime of the experiment a large and highly efficient cosmic ray veto (CRV) detector is needed. The CRV will cover the experimental apparatus with an area of approximately 330 m2. The overall efficiency must be no les than 99.99%, a requirement that must be maintained in the presence of intense backgrounds produced by proton and muon beams. The detector employs long scintillator strips with embedded wavelength shifting fibers, read out using silicon photomultipliers. Key features of the talk involve the design, fabrication, and performance of the CRV, along with an overview of the Mu2e experiment.

Special Seminar


Monday, January 27, 2020
3:30 PM
Physics Building, Room 204

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"Precision timing with the CMS MIP timing detector and search for new particle production at the LHC "


Matt Joyce , University of Virginia - Department of Physics
[Host: Brad Cox]
ABSTRACT:

The Compact Muon Solenoid (CMS) detector at the CERN Large Hadron Collider (LHC) is undergoing an extensive Phase II upgrade program to prepare for the challenging conditions of the High-Luminosity LHC (HL-LHC). In particular, a new timing layer will measure minimum ionizing particles (MIPs) with a time resolution of ~30ps and hermetic coverage up to a pseudo-rapidity of |η|=3. This MIP Timing Detector (MTD) will consist of a central barrel region based on LYSO:Ce crystals read out with SiPMs and two end-caps instrumented with radiation-tolerant Low Gain Avalanche Diodes. The precision time information from the MTD will reduce the effects of the high levels of pile-up expected at the HL-LHC and will bring new and unique capabilities to the CMS detector. The time information assigned to each track will enable the use of 4D reconstruction algorithms and will further discriminate interaction vertices within the same bunch crossing to recover the track purity of vertices in current LHC conditions.  We present motivations for precision timing at the HL-LHC and the ongoing MTD R&D targeting enhanced timing performance and radiation tolerance for the barrel layer components.  We will also describe the progress of our search for new physics in final states with two photons and missing transverse energy using the full Run2 dataset.  

Special High Energy Seminar


Thursday, November 14, 2019
4:00 PM
Physics Building, Room 204

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"Light in the Dark-Opening a new window to the Dark Sector "


Ruth Pottgen , Lund University
[Host: Craig Dukes]
ABSTRACT:

The origin and observed abundance of Dark Matter in the Universe can be explained elegantly by the thermal freeze-out mechanism, leading to a preferred mass range of the Dark Matter particles in the MeV-TeV region. The GeV-TeV mass range is being explored intensely by the variety of experiments searching for Weakly Interacting Massive Particles. The sub-GeV region, however, in which the masses of most of the building blocks of stable matter lie, is hardly being tested experimentally to date.
This mass range occurs naturally in Hidden Sector Dark Matter models. The Light Dark Matter eXperiment (LDMX) is a planned electron-beam fixed-target experiment, that has unique potential to conclusively test models for such light Dark Matter in the MeV to GeV range. This presentation will give an overview of the theoretical motivation, the main experimental challenges and how they are addressed as well as projected sensitivities.

SLIDESHOW:
High Energy
Wednesday, November 6, 2019
4:00 PM
Physics Building, Room 204

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"Searching for Dark Matter from the Lowest to the Highest Energies "


Bjoern Penning , Brandeis University
[Host: Bob Hirosky]
ABSTRACT:

Dark Matter (DM) is a long standing puzzle in fundamental physics and goal of a diverse research program.  In underground experiments we search for DM directly using lowest possible energy thresholds, at collider we seek to produce dark matter at the very highest energies, and with telescopes we look for telltale signatures in the cosmos. All these detection methods probe different parts of the possible parameter space. I will highlight status of existing and upcoming experiments including new direct detection experiments with world leading sensitivities to start data taking in early 2020. Finally  we’ll discuss how to connect these approaches and how an interdisciplinary program bridging experimental frontiers can provide the most stringent constraints.

 

High Energy
Wednesday, October 30, 2019
4:00 PM
Physics Building, Room 204

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"CNN Jet Image Tagging: from top measurements to new physics searches"


Dr. Kevin Nash , Rutgers University
[Host: Chris Neu]
ABSTRACT:

We detail the application of image recognition to jet tagging in CMS. The method is based on the CNN top tagging optimization seen in arXiv:1803.00107v1 and evolved to include additional color information, b tagging, and an adaptive zoom.  Additionally, we demonstrate how this jet tagging network can be decorrelated from the mass of the progenitor jet, which allows for the possibility of tagging BSM objects. We study the impact on top tagging sensitivity, the data-simulation agreement, and the versatility of the network to accept more exotic signatures.  Finally, we describe the application to the latest BSM physics searches.

Joint Nuclear/HEP seminar


Wednesday, July 24, 2019
3:30 PM
Physics Building, Room 204

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"Proton Spin at Small x"


Yuri Kovchegov , Ohio State
[Host: Peter Arnold]
ABSTRACT:

An integral part of the proton spin puzzle are the contributions to the proton spin coming from quarks and gluons having very small values of the Bjorken x variable. These contributions are mostly beyond the reach of current experiments and are very hard to calculate numerically on the lattice. It appears that better theoretical understanding of quark and gluon helicity distributions at small x is needed to assess the amount of proton spin coming from this region. In my talk I will describe the recent theoretical work aimed at finding the small-x asymptotics of the quark and gluon helicity distributions, along with their orbital angular momenta (OAM). I will derive small-x evolution equation for helicity and solve them to find the small-x asymptotics of the parton helicity distributions and OAM. The results of this work can be compared to the data to be collected at the upcoming Electron-Ion Collider (EIC) and can also be used to extrapolate the small-x helicity distributions to be measured at EIC to even smaller values of x, thus constraining the proton spin coming from small x.

High Energy
Wednesday, April 24, 2019
3:30 PM
Physics Building, Room 204

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"Light ring stability in ultra-compact objects"


Pedro Cunha , University of Lisbon
[Host: Kent Yagi]
ABSTRACT:

The following theorem is proven: axisymmetric, stationary solutions of the Einstein field equations formed from classical gravitational collapse of matter obeying the null energy condition, that are everywhere smooth and ultracompact (i.e., they have a  light ring, a.k.a. circular photon orbit) must have at least two light rings, and one of them is stable. It has been argued that stable light rings generally lead to nonlinear spacetime instabilities. Thus this result implies that smooth, physically and dynamically reasonable ultracompact objects are not viable as observational alternatives to black holes whenever these instabilities occur on astrophysically short time scales. The proof of the theorem has two parts: (i) We show that light rings always come in pairs, one being a saddle point and the other a local extremum of an effective potential. This result follows from a topological argument based on the Brouwer degree of a continuous map, with no assumptions on the spacetime dynamics, and hence it is applicable to any metric gravity theory where photons follow null geodesics. (ii) Assuming Einstein’s equations, we show that the extremum is a local minimum of the potential (i.e., a stable light ring) if the energy-momentum tensor satisfies the null energy condition.

High Energy
Wednesday, April 17, 2019
3:30 PM
Physics Building, Room 204

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"The Exterior Spacetime of Relativistic Stars in Quadratic Gravity"


Alexander Saffer , Montana State University
[Host: Kent Yagi]
ABSTRACT:

General Relativity (GR) has been the cornerstone of gravitational physics for a century. Over this time, numerous predictions and tests have strengthened the belief in GR as the foremost theory when discussing gravity. However, GR cannot in its present form be reconciled with either quantum mechanics, or many cosmological observations such as galactic rotation curves or the accelerated expansion of the universe. In an attempt to rectify these shortcomings, modified theories of gravity have been proposed. In this talk, I will present one of these theories and discuss my work in attempting to test its validity through the development of an exterior spacetime (metric) for a neutron star. From this, we expect to be able to develop a pulse profile which can be used, in conjunction with observations made of the x-ray flux of radiating neutron stars, to place constraints on the theory.

 

High Energy
Wednesday, April 10, 2019
3:30 PM
Physics Building, Room 204

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"Exploring light dark matter with the LDMX experiment"


Bertrand Echenard , Caltech
[Host: Craig Dukes]
ABSTRACT:

Understanding the nature of dark matter is a central objective of modern science, and recent theoretical developments have highlighted the importance of extending current searches over a wider range of masses. The Light Dark Matter eXperiment (LDMX) has been propose to search for light dark matter and sub-GeV New Physics in fixed-target electron-nucleus collisions with unprecedented sensitivity. The experiment is based on a missing momentum technique, in which dark matter is emitted by electrons scattering in a thin target, resulting in large missing momentum and energy in the detector. This talk will discuss the motivation for light dark matter and describe the LDMX concept and its expected performance.

SLIDESHOW:
Joint High Energy and Nuclear Seminar


Wednesday, April 3, 2019
3:30 PM
Physics Building, Room 204

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ABSTRACT:

The J-PARC TREK/E36 experiment with a stopped K+ beam is designed to provide a more precise measurement of the branching ratio RK = Γ(K+ → e+ν)/Γ(K+ → µ+ν) than previous in-flight K+ decay experiments. RK is very precisely predicted by the Standard Model (SM) with an uncertainty of 4×10−4 and any deviation from this prediction would very clearly indicate the existence of new physics beyond the SM. Additionally, the experiment is searching for dark photons/light neutral bosons (A0), which could be associated with dark matter or explain the gµ-2 anomaly and the proton radius puzzle. In the experiment, a K+ beam was stopped by a scintillating fiber target, and charged decay products were momentum analyzed and tracked by a 12-sector superconducting toroidal magnetic spectrometer and multi-wire proportional chambers (MWPCs) combined with a photon calorimeter with a large solid angle (75% of 4π) and 3 different particle identification systems. In this talk, the status of the RK and A0 analyses is presented, and the MWPC calibration and tracking by a Kalman filter are reported. This work has been supported by awards DE-SC0003884 and DE-SC0013941 in U.S., NSERC in Canada, and Kaken-hi in Japan.
 

High Energy
Wednesday, March 20, 2019
3:30 PM
Physics Building, Room 204

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"Neutrino Physics from the PROSPECT Experiment"


Christopher White, Ph.D. , Illinois Institute of Technology
[Host: Craig Dukes]
ABSTRACT:

PROSPECT, the Precision Oscillation and Spectrum Experiment, is a reactor antineutrino experiment designed to search for eV-scale sterile neutrinos and measure the spectrum of antineutrinos from highly-enriched 235U at the High Flux Isotope Reactor (HFIR). PROSPECT uses a 4-ton, segmented 6Li-doped liquid scintillator detector to make a high-resolution measurement of the prompt energy spectrum from inverse beta decay on protons. An optical and radioactive source calibration system integrated into the active detector volume is used to characterize the optical and energy response of all detector segments. I will discuss the calibration and characterization of the PROSPECT detector and report on PROSPECT’s first measurement of the energy spectrum associated with reactor antineutrinos.

Special Joint Nuclear and High Energy Seminar


Thursday, February 28, 2019
2:00 PM
Physics Building, Room 204

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"A New QCD Facility at the M2 beam line of the CERN SPS (COMPASS++/AMBER)"


Oleg Denisov , COMPASS experiment
[Host: Dustin Keller]
ABSTRACT:

Possibility to use high intensity secondary beams at the SPS M2 beam
line in combination with the world’s largest polarized target, liquid hydrogen,
liquid deuterium and various nuclear targets create a unique opportunity
for universal experimental facility to study previously unexplored aspects
of meson and nucleon structure, QCD dynamics and hadron spectroscopy. 

High intensity hadron (pion dominated) beams already made COMPASS the
world leading facility for hadron spectroscopy and  hadron structure
study through Drell-Yan production of di-muon pairs. High intensity
muon beams, previously used for unique semi-inclusive and exclusive
hard scattering programs, make possible proton radius measurement in
muon-proton elastic scattering and further development of polarized
exclusive hard scattering program.
  
Upgrades of the M2 beam line resulting in high intensity RF-separated
anti-proton- and kaon-beams would greatly expand the horizon of experimental
possibilities at CERN: hadron spectroscopy with kaon beam, studies
of transverse momentum dependent quark structure for protons, pions and
kaons, precise studies of nuclear effects and for the first time measurements
of kaon quark—gluon substructure.

High Energy
Tuesday, January 15, 2019
4:00 PM
Physics Building, Room 204

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"TBA"


Reserved
ABSTRACT:

TBA

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