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Lunchtime Seminars

Tuesdays ~ 12pm ~ Kolker Room, 26-414

 

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



February 9, 2016

 

Gunther Roland, MIT

Jet physics in the 2020's with CMS and sPHENIX

The strongly interacting quark-gluon plasma produced in ultrarelativistic heavy ion collisions at RHIC and LHC is, by some measure, the most perfect known fluid. Understanding how this near-perfect fluidity arises from the underlying interactions of quarks and gluons is one of two main goals of heavy ion experiments at RHIC and LHC in the next decade and beyond. Multi-scale probes such as high pT jets and different quarkonia states are the key diagnostic tools in these studies. I will discuss the approach of the MIT heavy-ion group to this program using the CMS@LHC and proposed sPHENIX@RHIC experiments.

 

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

(Lunch will be served at 11:50.)



February 16, 2016

 

Or Hen, MIT

Tabletop Tests of the Standard Model @ MIT

High precision measurements of nuclear decays are one of the most precise tools for probing physics beyond the standard model. High precision measurements at low energies indirectly probe physics at very high energies, rivaling that of the largest accelerators, while still remaining a relatively inexpensive research program. 

In this talk I will present two new experiments been setup at MIT to search for CP violations in positronium decay and to study the neutrino-beta correlations in 8Li decay. The experiments will utilize state-of-the-art detector technology, such as digital silicon photomultipliers and TPCs, to improve systematics and increase statistics and kinematical coverage as compared to previous studies. I will present these technologies and their possible application in various nuclear and particle physics experiments.

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

(Lunch will be served at 11:50.)

 


 


February 23, 2016

 

Adrien Hourlier, Universite Paris Diderot

Fast Neutron Detection with DCTPC

Fast Neutrons represent a major background for low background experiments, such as shallow reactor neutrino experiments and dark matter experiments. Neutron flux measurements have been carried out by the KARMEN2 experiment at the surface, KamLAND at 2700 m.w.e. and by LVDS at 3200 m.w.e. but a gap persists for shallower experiments.
A low-pressure gaseous TPC was developed to measure the fast neutron spectrum in Double Chooz underground halls. Neutron scatterings are detected through the ionization track to the nuclear recoil of helium present in the vessel, projected on an anode plane. The use of a CCD to image the anode plane provides 2D information. The vertical projection can be accessed by recording the waveforms of the charge read out on the anode plane and ground mesh. Using this technique, the energy of an event can be reconstructed with a precision of the order of ~2%.
Located in both experimental halls of the Double Chooz experiment, DCTPC provides measurements at shallow depths, with 120 m.w.e. and 300 m.w.e. shielding. The two experimental conditions allowed us to observe the change in the relative proportions of the two major neutron production
mechanisms, spallation from cosmic muons and ambient radioactivity.

 

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

(Lunch will be served at 11:50.)


 


March 1, 2016

 

Gabriel Collin, MIT

Status of Global Sterile Neutrino Fits

Tension among short baseline neutrino experiments has pointed toward the possible need for one or more additional mass splittings in the existing neutrino oscillation framework. This would require the addition of at least one sterile (non-interacting) neutrino to the current model. I will introduce models with one, two, and three sterile neutrinos. The parameters of these models can be constrained with fits to global data. I will present the results of the latest update to our fitting effort, and review future experiments that can address the question.

 

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

(Lunch will be served at 11:50.)



March 8, 2016

 

Itaru Nakigawa, RIKEN/RBRC

First Asymmetry Measurements in High-Energy Polarized
Proton-Nucleus Collision at PHENIX-RHIC

The relativistic heavy ion collider (RHIC) has been operated for heavy ion + heavy ion, heavy ion + light ion, and polarized proton + proton collisions since 2001. This unique facility has provided many new insights, particularly in regards to the quark gluon plasma (QGP) and in the understanding of proton spin structure. In the last year (Run15), we executed the first attempt to collide polarized protons on heavy nuclei at the collision energy of  s   = 200 GeV. Since the proton beam in LHC is not polarized, any asymmetry measurements utilizing proton polarization will be at the energy frontier, since all existing polarized p-A experiments were carried out using fixed nuclear targets, and therefore at one order of magnitude lower in center-of-mass energy.
I will present the very first single transverse spin asymmetry AN results of forward neutron production observed in PHENIX from Run15. The finite single spin asymmetry in the forward neutron production in polarized proton-proton scattering was discovered several years ago in PHENIX. The asymmetry was unexpectedly large, i.e. several percent. Later, it was well reproduced by the interference of π and a1-Reggeon exchange amplitudes. The resulting dependence of AN on nuclear mass number has turned out to be surprisingly strong and is totally unexpected in the existing theoretical framework. I will discuss possible effects of the observed asymmetries including electromagnetic interactions, which could be neglected in proton-proton case.

 

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

(Lunch will be served at 11:50.)



March 15, 2016

 

Yotam Soreq, MIT

Probing the Higgs and New Physics with Isotope Shift

We propose to use precision measurement of isotope shift in atomic clock transitions to probe physics beyond the standard model as well as to probe the Higgs boson coupling the the electron and up and down quarks. We show that the attractive Higgs force between nuclei and their bound electrons induces measurable non-linearities in a King plot of two isotope shifts. We present an experimental method which, given state-of-the-art accuracy in frequency comparison, competes with and potentially surpasses the Large Hadron Collider in bounding the Higgs-to-light-fermion couplings. Better knowledge of the latter is an important test of the Standard Model which could lead, besides the establishment of new physics above the weak scale, to an alternative understanding of the flavor puzzle. Moreover, we derive the reach for generic new physics above the GeV scale at the effective field theory level, as well as estimate the limits on possible new spin-independent forces mediated by sub-GeV states coupled to electrons and neutrons. We also study the weak force and show that isotope shifts could provide strong constraints on the Z couplings to valence quarks, which complement precision observables at LEP and atomic parity violation experiments.

 

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

(Lunch will be served at 11:50.)



March 22, 2016

 

No Seminar

Spring Break


 


March 29, 2016

 

Chris Marshall, University of Rochester

Kaon Production by neutrinos at MINERvA

Charged kaon production by atmospheric neutrinos is a background in searches for the proton decay p → K+ v̅ . The MINERvA neutrino-nucleus cross section experiment uses timing information to identify K+ decay-at-rest events. I will present the first differential cross section measurements for both charged- and neutral-current neutrinoproduction of K+, and discuss how these measurements can be used to constrain background predictions in proton decay searches. I will also show the first experimental evidence for coherent K+production by neutrinos.

 

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

(Lunch will be served at 11:50.)



April 5, 2016

 

Brian Naranjo, UCLA

Dielectric laser acceleration: the intersection of photonics and high
field physics

Acceleration gradients in excess of 1 GeV/m, sustained over
significant distances while yielding high quality electron beams, have
yet to be demonstrated, but they are the goal of much recent work in
accelerator physics. The immediate application of such a development
would be toward university-scale x-ray free-electron lasers (XFEL).


Currently, only large accelerator facilities host these important
research tools, for example LCLS at SLAC and FLASH at DESY. One
candidate for such an accelerator is the dielectric laser accelerator
(DLA), whereby strong optical fields both confine and accelerate an
electron beam. Described in terms of accelerating "buckets,'' the
dynamics of electrons in a GV/m optical field are analogous to the
intricate dynamics of ions in an rf linac. I present the current
status of DLA design at UCLA's Particle Beam Physics Lab (PBPL).


Topics covered will be: beam focusing dynamics, photonic design,
parallel laser coupling, phase space manipulations, adiabatic bunch
compression, and device fabrication.

 

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

(Lunch will be served at 11:50.)


April 12, 2016

 

Kanika Sachdev, Fermi National Accelerator Laboratory

First Oscillation Results from the NOvA Experiment

NOvA is a long-baseline neutrino oscillation experiment optimized for electron neutrino appearance in the NuMI beam, a muon neutrino source at Fermilab. It consists of two functionally identical, nearly fully-active liquid-scintillator tracking calorimeters. The near detector (ND) at Fermilab is used to study the neutrino beam spectrum prior to standard oscillations and the far detector, 810 km away in Northern Minnesota, observes the oscillated beam and is used to extract oscillation parameters from the data. NOvA's long baseline, combined with the ability of the NuMI beam to operate in the anti-neutrino mode, makes NOvA sensitive to the last unmeasured parameters in neutrino oscillations- mass hierarchy, CP violation and the octant of mixing angle theta_23. In this talk, I will present the first neutrino oscillation results from the NOvA experiment.

 

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

(Lunch will be served at 11:50.)


 

April 19, 2016

 

Matt Sievert, BNL

Studying Short-Range Nucleon-Nucleon Interactions with an EIC

The innermost repulsive core of the nucleon-nucleon potential, essential for the stability of nuclei, remains an elusive property of first-principles QCD. High-energy elastic nucleon-nucleon scattering (at fixed center-of-mass angle) probes such a regime, but experiment reveals a surprising flavor dependence for such processes, leading to the well-established "quark counting rules." The implication that quark exchange dominates over gluon exchange in the hard process confounds the usual pQCD power counting, which suggests that gluon exchange (the "Landshoff mechanism") should be parametrically dominant over quark exchange. Still more intriguing, QCD permits two nucleons at very short distances to contain exotic configurations of quarks such as "hidden color" states, in which the 6 valence quarks are grouped into two "nucleons" which separately carry an octet color charge, but are color neutral overall. In some simple estimates these exotic states could contribute as much as 80% of the 6-quark state, yet experimentally hidden color states in nuclei have been excluded down to the few-percent level.

In this talk, I will propose a new process accessible at a future electron-ion collider (EIC) which is sensitive to these very short range nucleon-nucleon interactions: the exclusive electroproduction of vector mesons off a deuteron target, in which the deuteron breaks up into a proton-neutron pair with large transverse momentum. This process is a generalization of exclusive meson production on the proton as measured at HERA, which can be described in QCD in terms of nonperturbative matrix elements known as "generalized parton distribution functions" (GPD's). For the case of a deuteron breaking up into a proton/neutron pair, the "transition GPD" depends on an additional internal momentum scale: the relative momentum of the final-state nucleons. I will argue that when this momentum scale is large, it becomes possible to extract information about the short-distance pQCD rescattering of the nucleons. Using a toy model first as a proof of principle, I will then estimate the rates for realistic nucleons to show that this process would be accessible at a future EIC. Such an analysis, which is only possible at a high-luminosity EIC, would be complementary to studies of elastic nucleon-nucleon scattering and may shed new light on the QCD content of two nucleons at very short distances.

 

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

(Lunch will be served at 11:50.)


April 26, 2016

 

Ben Safdi, MIT

Cosmic Axion Detection with an Amplifying B-field Ring Apparatus

When ultralight axion dark matter encounters a static magnetic field, it sources an effective electric current that follows the magnetic field lines and oscillates at the axion Compton frequency. I will describe a new idea for a laboratory experiment to detect this axion effective current. In the presence of axion dark matter, a toroidal magnet will act like an oscillating current ring, whose induced magnetic flux can be measured by an external pickup loop inductively coupled to a SQUID magnetometer. I will demonstrate that a meter-scale toroid could potentially probe the QCD axion with a GUT-scale decay constant, and I will describe ongoing efforts at MIT to build a small-scale prototype, with a toroid of O(10 cm).

 

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

(Lunch will be served at 11:50.)


May 3, 2016

 

Adam Aurisano, University of Cincinnati

Using Modern Deep Learning Techniques to Categorize Neutrino Interactions

A core problem in experimental high-energy physics is the correct categorization of particle interactions recorded in our detectors as signal or background. This characterization is commonly done by reconstructing high-level components such as clusters, tracks, showers, jets, and rings within the event topology recorded by the detector and summarizing the energy, directions, and shape of these objects with a small number of quantities. These are often then fed into multi-variate algorithms to produce a final selector. However, these techniques are highly sensitive to the quality of the reconstruction of the high-level features and our imagination in developing them. Recent advances in deep learning have created new classes of machine learning algorithms which are capable of learning features from raw data, avoiding the pitfalls associated with high level reconstruction. In particular, convolutional neural networks, which automatically learn features from raw data, have been very successful in both the computer vision and natural language processing communities. Due to the spatial segmentation of sampling calorimeters, many high energy experiments can take advantage of CNN technology to identify events. In particular, I will discuss the specific application to the NOvA neutrino detector. This algorithm, known as CVN (Convolutional Visual Network), identifies neutrino events based on their topology without the need for detailed event reconstruction and outperforms algorithms currently
in use by the experiment.

 

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

(Lunch will be served at 11:50.)


May 10, 2016

 

TBA

TBA

TBA

 

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

(Lunch will be served at 11:50.)