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Lunchtime Seminars

Tuesdays ~ 12pm ~ Kolker Room, 26-414

 

Committee:
Gunther Roland, Chair ~ Doug Hasell~ Paolo Zuccon



 

September 9, 2014

 


Matteo Cremonsi, University of Chicago

Observation of s-channel single-top-quark production at the Tevatron

Abstract: Studies of the properties of the top quark are being actively pursued at the Fermilab's Tevatron and at the CERN LHC. Besides top-antitop pair production by strong interaction, which is the most common production mechanism, the less common single-top production via electroweak interaction is now being tackled.

 

Collisions that produce a single top quark through the weak nuclear force are rarer, and the events are much less distinctive than top pairs. According to the Standard Model, single-top production can be induced by several amplitudes. Production through the exchange of a virtual W boson in the s-channel is very hard to isolate. This production channel is barely accessible at the Tevatron and is presently out of reach at the higher energy LHC. On the other hand, new physics effects might most readily show up in this channel. The observation of this production channel was one of the ultimate goals of the Tevatron.

 

The analysis methods adopted by the CDF and D0 experiments to isolate s-channel single-top quark production will be described. The speaker will illustrate the main analysis features, underling the challenges and describing the techniques employed in order to accomplish such a difficult task. The CDF and D0 results will be shown, claiming discovery by combining them.

time:    Noon
place:   Kolker Room (26-414)

(Lunch will be served.)



September 16, 2014

 


Ross Corliss, MIT

Looking for Dark Light

Abstract: At this point, the existence of every particle in the Standard Model has been experimentally confirmed, but we know this is not the end of the story. The DarkLight experiment will search for a beyond-the-standard-model dark photon, A', that could shed light on some apparent shortcomings, both the large-scale absence of dark matter in the theory, and the small-scale deviation of the muon magnetic dipole moment calculation from recent measurements. Using the intense electron beam at Jefferson Lab's Energy Recovering Linac (the former FEL), DarkLight will look for A' production by reconstructing complete final states in extremely high-rate (1036/cm2/s) electron-proton collisions. High-speed readout will make all of this data available, allowing DarkLight to probe several different A' signatures. I will discuss the experimental design and the challenges of operating at such high rates, as well as how these measurements will fit into the ongoing search for phenomena outside of the Standard Model.

time:    Noon
place:   Kolker Room (26-414)

(Lunch will be served.)



September 23, 2014


Alexander Himmel, Duke University

Short-baseline Oscillation Measurements with Electron Neutrinos at T2K

Abstract: The T2K experiment has searched for disappearance at a short baseline in the electron neutrino component of the JPARC neutrino beam consistent with oscillations to a sterile neutrino. Anomalies in the previous measurements of electron neutrinos and antineutrinos from reactors and radioactive sources are not explained by oscillations among three neutrinos, but are instead compatible with the existence of a fourth neutrino mass eigenstate with a mass-splitting at or above 1 eV2 relative to the active neutrinos. These anomalies are tested with the T2K near detector, ND280. Located 280 m from the hadron production point with an average electron-neutrino energy of 500 MeV, this experiment is sensitive to sterile oscillations with a mass difference of ~2 eV2. The analysis of the electron-neutrino interaction rates, combined with a good understanding of the backgrounds allows us to constrain the oscillation parameter space and to reject some regions of parameter space allowed by the gallium and reactor anomalies.

time:    Noon
place:   Kolker Room (26-414)

(Lunch will be served.)



September 30, 2014


Laura Fields, Northwestern University

Neutrino Scattering Results from MINERvA

Abstract: High precision measurements of neutrino interaction cross sections are crucial to current and future neutrino oscillation experiments that hope to measure CP violation.  The MINERvA experiment at Fermilab was designed to make such measurements.  First results from MINERvA for a variety of processes, including charged current quasi-elastic scattering, coherent and inclusive pion production, and inclusive charged current interactions on different nuclei, are now available.  A selection of these new results and prospects for future cross section measurements with MINERvA will be discussed.

 

time:    Noon
place:   Kolker Room (26-414)

(Lunch will be served.)



October 7, 2014


Si Xie, Caltech

Higgs Boson Properties, Couplings and Tensor Structure in the
Four-Lepton Golden Channel

Abstract: The discovery of the Higgs boson brings with it a new era in elementary particle physics. Besides being the key to the mechanism of electroweak symmetry breaking and to the generation of fermion masses, the observation of the Higgs boson represents the first time in the history of particle physics that an elementary spin-0 particle has been seen. I will discuss measurements of various properties of this unique particle including recent measurements and constraints of the tensor structure and anomalous couplings of the Higgs boson in the four-lepton channel, as well as future prospects for precision measurements at the LHC.

 

time:    Noon
place:   Kolker Room (26-414)

(Lunch will be served.)



October 14, 2014

 

Tammy Walton, Fermi National Accelerator Laboratory

Recent Results of Quasi-Elastic Scattering at MINERvA

Abstract: MINERvA is a neutrino-nucleus cross section experiment in the NuMI beamline at Fermilab. The MINERvA detector consists of fine-grained plastic scintillator (CH) for high resolution tracking and calorimetry, and therefore is able to reconstruct exclusive final states. MINERvA is currently producing cross section measurements for both inclusive and exclusive neutrino interactions. Presented are the recent measurements from quasi-elastic scattering, which has a simple final-state topology and generally, is modeled using the relativistic Fermi gas. In addition, is known as the "standard candle" for neutrino oscillation experiments.

For scattering from nuclei with A > 2, the predicted cross section is inconsistent with the relativistic Fermi gas nuclear model and this discrepancy is often explained by considering the correlations between nucleons. In addition, the particle transportation through the nucleus is described by a particle cascade prescription. It has been observed that contributions from nuclear effects and final state interactions add to the measure quasi-elastic cross section. Contributions to the cross section from these type of events must be precisely model in the neutrino generators, because nuclear effects and final state interactions influence the estimate of the neutrino energy used by precision neutrino experiments.

time:    Noon
place:   Kolker Room (26-414)

(Lunch will be served.)

 



October 21, 2014


Alex Barbieri, MIT

Jet measurements in Heavy Ion Collisions with CMS: Results from Run 1 and Opportunities for Run 2

Abstract: Jets are sensitive probes of the Quark Gluon Plasma formed in heavy ion collisions at the LHC and RHIC. A series of measurements of jets with the CMS detector are presented which explore the transfer of energy to the medium and the modification of jets with respect to pp and pA collisions, including the modification of gamma-jet partners and the distribution of transverse momentum along the jet axis. The confirmation of jet quenching leads to a study of where the quenched energy is transported to. A brief discussion of the increase of statistics planned for Run 2 will explain the exciting prospects for extensions to these jet measurements.

 

 

time:    Noon
place:   Kolker Room (26-414)

(Lunch will be served.)



October 28, 2014


Ning Zhou, University of California, Irvine

Dark Matter Searches at ATLAS

Abstract: Different approaches to finding evidence for dark matter at the LHC are presented. These include searches for events with large missing transverse momentum and a photon or W/Z boson. Different interpretations of the results are presented, including effective field theories and explicit mediator models. Results from sqrt(s) = 8 TeV data taking are presented. A new searching channel is also proposed to constrain the Higgs-portal dark matter model.

 

time:    Noon
place:   Kolker Room (26-414)

(Lunch will be served.)



November 4, 2014


Dragos Velicanu, MIT

Collective behavior of the hottest, densest matter in the universe with CMS

Abstract: The LHC produces some of the hottest and densest matter in the universe. This matter is postulated to be made of deconfined quarks and gluons in a strongly coupled state that exhibits collective behavior. This can be measured experimentally by observing the azimuthal distribution of energy and two particle correlations in the detector. Recently this collective behavior has been observed in proton proton and proton nucleus collisions as well which brings our understanding of the underlying physics into question and hints at the existence of this type of matter in much smaller states.

 

time:    Noon
place:   Kolker Room (26-414)

(Lunch will be served.)



November 11, 2013

week of VETERANS' DAY – No Lunchtime Seminar



November 18, 2014


Wilke van der Schee, MIT

Strong Coupling QGP Thermalization with Longitudinal Dynamics

Abstract: This talk will give an overview of recent attempts to use holography to understand the thermalization of heavy-ion collisions. For this I will briefly review the current status of heavy-ion collisions, and argue that the AdS/CFT duality may improve our understanding of some aspects of these collisions. After this I will highlight some of my recent work, in particular focusing on the longitudinal dynamics in a heavy ion collision, which may provide a distinctive way to probe the results from these strong coupled methods. In the end I will show some very preliminary results allowing to make a direct comparison with experimental data.

time:    Noon
place:   Kolker Room (26-414)

(Lunch will be served.)



November 25, 2014


Bodhitha Jayatilaka, MIT/FermiLab

Rumors of Our Demise: The Long Tail of Physics from CDF

Abstract: In the three years since the shutdown of the Tevatron collider, its two experiments, CDF and D0, have continued to produce physics results. I will given an overview of the post-Tevatron CDF physics program, highlighting results from this year. Results cover top quark, electroweak, QCD, and heavy flavor physics. I will also discuss the potential for future physics results using the Tevatron dataset and the data preservation program that plans for this possibility.

 

time:    Noon
place:   Kolker Room (26-414)

(Lunch will be served.)



December 2, 2014


Marc Weber, Columbia University

Direct Dark Matter Search on the Verge of a New Detector Generation – Moving from XENON100 to XENON1T and Beyond

Abstract: The XENON dark matter project aims at finding direct evidence for the scattering of weakly interacting massive dark matter particles (WIMPs) with target nuclei in an ultra-low background liquid xenon detector. After the successful operation of the XENON100 instrument – the world’s most sensitive deep underground WIMP detector for many years until late 2013 – the next generation detector XENON1T is presently being built at the Italian Gran Sasso underground facility and expected to start operation in 2015.

 

At the same time, calibration measurements to complete our understanding of signal creation from electronic and nuclear recoils in liquid xenon targets are ongoing – both in small scale detectors, like the one operated by the Columbia University group, and in XENON100.  

 

The talk will cover recent science results from the current generation XENON100 experiment and present the fast progress made in the construction of the new detector. Looking even further ahead into the future, the scientific reach of XENON1T and potential upgrades will be discussed. Another focus will be the ongoing determination of charge and light yield as a function of applied electrical drift field, currently being measured for gamma-ray interactions in the small scale TPC setup at Columbia University Nevis Labs.

time:    Noon
place:   Kolker Room (26-414)

(Lunch will be served.)



December 9, 2014


Renee Fatemi, University of Kentucky

Constraining Quark Transversity Through Transverse Spin Asymmetry Measurements at STAR

Abstract:

abstract

time:    Noon
place:   Kolker Room (26-414)

(Lunch will be served.)