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Lunchtime Seminars
Tuesday ~ 12pm ~ Kolker Room, 26-414
February 7, 2012
Eoin Butler
CERN
"Cooling trapped antihydrogen -- towards precision spectroscopy and gravity"
Antihydrogen, the antimatter partner of hydrogen, holds the promise of sensitive tests of fundamental symmetries, including the Charge-Parity-Time theorem and the Weak Equivalence principle of general relativity.
The ALPHA experiment, based at CERN, is working to make precision spectroscopic measurements comparing the spectra of hydrogen and antihydrogen.
Recent progress in the field has been rapid -- I will present ALPHA's results demonstrating the confinement of antihydrogen atoms in a magnetic minimum trap for up to 1,000 s, as well as the particle preparation and control techniques that were needed to achieve this.
Now that antihydrogen can be trapped, the focus is shifting to spectroscopic measurements.
The first measurements will be crude, limited by the temperature of the atoms (around 0.5 K) and the highly inhomogeneous magnetic fields needed to confine them.
Attaining higher precision will hinge on the ability to cool antihydrogen.
Experimentally realising this will be challenging, requiring the demonstration of techniques and technologies that have yet to be developed.
I will present a proposal for cooling antihydrogen to the millikelvin level, where an experiment to measure the gravitational behavior of trapped antihydrogen can be carried out.
HOST: R. Milner
February 14, 2012
Jahred Adelman
Yale University
"An excess of needles in the haystack? The hunt for new physics at ATLAS"
Just after the end of the LHC's 2011 pp run, ATLAS is performing a wide range of searches for new physics beyond the Standard Model. I'll discuss a select few of the newest and most exciting results from the ATLAS exotics group, particularly several signature-based searches in topologies that are rare in the Standard Model. The talk will end with some prospects for analysis of the full 2011 dataset and the 2012 pp run as well as longer-term plans for finding new physics at the LHC.
HOST: C. Paus
February 21, 2012
Jesse Wodin
SLAC
"The search for neutrinoless double beta decay with the EXO experiment"
The Enriched Xenon Observatory (EXO) is a series of experiments designed to search for the neutrinoless double beta decay (0nbb) of Xe-136. Observation of 0nbb would determine an absolute mass scale for neutrinos, prove that neutrinos are massive Majorana particles (indistinguishable from their own antiparticles), and constitute physics beyond the Standard Model. The current phase of the experiment, EXO-200, is operating and serves as a prototype for the 1-10 ton scale full-EXO experiment. I will report on our recent observation of the two-neutrino (2nbb) decay mode in Xe-136 with T_1/2 = 2.11 +- 0.04 (stat.) +- 0.21 (sys.) x 10^21 yr. This second order process, predicted by the Standard Model, has been observed for several nuclei but not for Xe-136. Additionally, I will discuss current R&D towards the full-EXO experiment that combines aspects of nuclear and atomic physics, and touch upon my other research plans in neutrino physics.
HOST: P. Fisher
February 28, 2012
Yen-Jie Lee
MIT
"Little big bang: Relativistic Heavy Ion Collisions"
Heavy-ion collisions at LHC produce QCD matter with
extremely large energy density, allowing us to access
the region of the QCD phase diagram governed by partonic
degrees of freedom, the Quark-Gluon Plasma (QGP).
This unique state of matter is similar to the
trillion degree medium that filled the early universe
shortly after the Big Bang.
The energy loss of fast partons traversing this strongly interacting
matter is one of the most interesting observables to probe the nature
of the QGP. The multipurpose Compact Muon Solenoid (CMS) detector is
well designed to measure high pT probes such as jets and photons with
its high resolution calorimeters and high precision silicon tracker.
New ideas and results using those high pt probes have brought us a new
picture of the in-medium parton energy loss mechanism and provided
important insights into the properties of the QGP.
HOST: W. Busza
March 20, 2012
Joshua Spitz
MIT
"Probing the neutrino with liquid argon"
The ArgoNeuT Liquid Argon Time Projection Chamber (LArTPC) experiment has collected thousands of neutrino and anti-neutrino events in the NuMI beamline at Fermilab. ArgoNeuT's first physics results will be presented. The results are relevant for long baseline neutrino oscillation experiments searching for non-zero theta13, CP-violation in the lepton sector, and the sign of the neutrino mass hierarchy, among other things. These measurements, elucidating the nature of the neutrino-nucleus interaction, represent a significant step forward for LArTPC technology as they are among the first neutrino physics results with such a device.
HOST: J. Conrad
April 3, 2012
Jorge Diaz
Indiana University
"Lorentz symmetry and neutrinos"
Lorentz symmetry is a cornerstone of modern physics. As the spacetime symmetry of special relativity, Lorentz invariance is a basic component of the standard model of particle physics and general relativity, which to date constitute our most successful descriptions of nature. Deviations from exact symmetry would radically change our view of the universe and current experiments allow us to test the validity of this assumption. Neutrinos, on the other hand, are neutral fundamental particles that barely interact with matter. Even though we have learned how to detect them and measure some of their properties, the ghostly nature of these particles continues to defy our theories.
In this talk, I will describe how we can use current and future neutrino experiments to search for possible violations of Lorentz invariance. I will also show how the breaking of Lorentz invariance could explain some anomalous results that different experiments have observed in recent years.
HOST: J. Conrad
April 10, 2012
Brian Daub
MIT
"Low Energy Neutron-Proton Interactions"
There have been few measurements of cross sections for neutron-proton scattering and radiative capture below 1 MeV. Those measurements which do exist are at a small number of energies, and are inconsistent with theoretical models and with each other. Several experiments were conducted with the goal of obtaining improved data on these cross sections at the University of Kentucky (UKY) and Los Alamos Neutron Science Center (LANSCE): feasibility studies for measuring the low energy cross section for n − p radiative capture; measurements of the response of BC418 plastic scintillator to low energy protons, yielding very precise results from 100 keV to 3.6 MeV; and measured of the total cross section for n − p scattering by absorption from 150 to 800 keV, filling in a significant gap in the total cross section data below 500 keV. I will present the methods and results of these experiments, and discuss future planned measurements of these low energy interactions.
HOST: J. Matthews
April 24, 2012
Ron Moore
Massachusetts General Hospital
"Smashing Atoms for Discovery and Medicine"
The large particle accelerators for high energy physics experiments fascinate scientists and the general public with their size and complexity. But there are thousands of smaller accelerators in use around the world for more practical industrial and medical applications. I will discuss the connections between high energy physics machines and accelerators used in medicine, as well a couple of medical applications performed every day in hospitals.
HOST: S. Nahn
May 1, 2012
Kendall Mahn
TRIUMF
"A search for short-baseline muon neutrino disappearance with MiniBooNE and SciBooNE"
Neutrino mixing is consistent with three generations of neutrinos and a unitary mixing matrix. However, there is tension between the LSND experiments result of antineutrino oscillation at short baseline and the lack of such observation with the analogous result of the MiniBooNE experiment with neutrinos, indicating a possible third $\Delta m^2$ around 1$eV^2$ due to more than three neutrino generations or other exotic physics. A complementary way to access the same physics as $\nu_e$ appearance is $\nu_{\mu}$ disappearance. The MiniBooNE-only $\nu_{\mu}$ and $\overline{\nu}_{\mu}$ disappearance search was limited by flux and cross section uncertainties, which are reduced with the addition of data from the SciBooNE experiment, also present in the Fermilab Booster Neutrino beamline. This talk will describe the current picture of short-baseline neutrino disappearance, the flux constraint provided by SciBooNE, and the status of the joint MiniBooNE-SciBooNE analysis.
HOST: J. Formaggio
May 8, 2012
Alice Ohlson
Yale
"Jet-hadron correlations in STAR"
At RHIC, the study of dihadron correlations has been one of the primary methods used to investigate the propagation and modification of hard-scattered partons in the QGP. Due to recent advancements in jet-finding algorithms it is now possible to use reconstructed jets as triggers in these correlation studies. I show results of a systematic study of jet-hadron correlations in 200 GeV p+p and central Au+Au collisions. It is observed that the associated hadron yield of the awayside jet is significantly suppressed in Au+Au compared to p+p at high transverse momentum, and energetically balanced in large part by enhancement at low transverse momentum. A significant source of systematic uncertainty in the jet-hadron correlations analysis is the subtraction of the combinatoric background, since jet v2 and jet v3, which describe the correlations of the jet axis with the second- and third-order participant planes, are unknown. In this talk I discuss progress towards measurements of jet vn.
HOST: G. Roland
May 15, 2012
Todd Adams
Florida State Univeristy
"Searching for Massive, Charged Particles at CMS"
A long-lived, massive charged particle produced at the LHC would leave distintive signatures in the collider detectors, namely large ionization energies and long time-of-flight. I will present results from the CMS Collaboration that use such signals to search for new particles. Charged particles are a generic signature predicted by many different extensions of the standard model. However, uncertainties in the interaction models can modify the signatures, therefore we use several different analyses. We apply our search to several theories including supersymmetry and a new vector-like confinement model.
HOST: J. Conrad
May 22, 2012
Brad Filippone
CalTech
"Measuring Neutron Decay with Ultra-Cold Neutrons"
Neutrons with velocities less than ~ 5 m/s can be efficiently trapped in material bottles. These Ultra-Cold Neutrons (UCN) allow precision measurement of neutron decay properties. In particular, the UCNA experiment has measured the the nucleon's weak axial-vector coupling constant for the first time with UCN at the LANSCE facility in Los Alamos National Lab. I will discuss the novel aspects of this experiment along with the impact of present and future precision results.
HOST: J. Formaggio
Committee
Joseph Formaggio (Chair), Steve Nahn, Gunther Roland
