Indiana University High Energy Physics
and Astrophysics Seminars
2001-2002 Academic Year
| Mondays, 4pm | Refreshments 3:30 pm |
| Swain West 238 | HEP Coffee Room (SW262) |
Spring Semester 2002
| Jan. 7: | Simulation of the ATLAS TRT Detector |
| Fred Luehring | |
| Indiana U.
Monte Carlo simulation has played an important role in the development of the
ATLAS Transition Radiation Tracker (TRT). This talk will discuss an overview
of the simulation work to study the response of the TRT to the very high rates
of charged particles expected at LHC and its ability to identify electrons.
It will also cover the conversion of the ATLAS software into object oriented
(OO) C++ code and the evolution of the overall ATLAS offline software
framework.
|
| Jan. 21: | Baryon Resonances and Strong QCD |
| Eberhard Klempt | |
| U. Bonn
Baryon resonances lie on Regge trajectories. It is shown that baryon masses
depend strongly on their intrinsic orbital angular momenta while there is
little or no evidence for spin-orbit interactions. Spin-spin interactions are
induced by instanton forces with no significant contributions from magnetic
hyperfine interactions. Based on these experimental observations, a new mass
formula is proposed which reproduces (nearly) all baryon resonance masses.
The mass formula uses four parameters. The success of the new mass formula suggests a new concept of constituent quarks. The model reduces largely the number of `missing resonances', and sheds new light on the spin crisis of the nucleon.
|
| Jan. 22:
Tuesday |
Preons and Fibers: Tales from the Front |
| Don Lincoln | |
| Fermilab
Operations at the Fermilab Tevatron are commencing, after a five year
hiatus. In order to absorb the data, now produced at a
much-accelerated rate, the D0 detector has recently completed an
upgrade of its detector subsystems. The most notable overhaul is the
complete replacement of its tracking system with a new tracker
consisting of scintillating fiber, read out by Visible Light Photon
Counters. This talk will detail some of the technology, construction
details and operational experience with this new detector.
Of course the point of the D0 detector is to increase our physics knowledge and many topics are currently under study. One exciting topic is the prospect that the 'generation-structure' of quarks and leptons heralds the existence of a lower state of matter. This talk will detail the state of knowledge in quark and lepton compositeness from Run I and give the audience a taste of Run II's plans and possible discovery reach.
|
| Jan. 28: | Search for gluonic excitations, results of the Crystal Barrel experiment |
| Ulrike Thoma | |
| U. Bonn
The possibility that gluonic excitations of hadronic matter
or of the QCD vacuum exist is perhaps the most fascinating topic in hadron spectroscopy. Lattice gauge theories predict a whole spectrum of glueballs (bound states of gluons) and hybrids (bound states of a quark, antiquark and a gluon). The search for these states was one of the aims of the Crystal Barrel experiment at LEAR. In lattice gauge theories the lightest glueball is predicted to have scalar quantum numbers and a mass of about 1600 MeV/c^2. The observation of more scalar isoscalar mesons than the quark model can host has led to speculations that a glueball of mass of about 1600 MeV/c^2 has intruded into the spectrum of scalar quarkonia and mixes with them, thus producing the states observed in the mass range below 2 GeV/c^2. Experimental information on the number of existing scalar states and on their decay modes may be crucial for the understanding of the scalar mesons and may clarify the possible existence of the scalar glueball. Another question of interest is the existence of hybrids, of mesons in which the flux tube mediating the interaction between quarks and antiquarks has been excited. In general hybrids can also mix with normal mesons making their identification difficult. But hybrids can also have exotic quantum numbers, which cannot be reached by quark-antiquark systems. States with exotic quantum numbers were recently discovered by E852 at BNL and by Crystal Barrel.
|
| Jan. 30:
Wednesday 12:15PM SW113 |
Searching for SUSY at Tevatron and LHC |
| Yili Wang | |
| U. Hawaii
We examine signals for sparticle production at the Fermilab Tevatron and CERN
LHC within the framework of gauge-mediated supersymmetry breaking
(GMSB) and inverted mass hierarchy models (IMH). Within GMSB, we analyse
several model lines, each of which leads to a qualitatively different
signature, and quantify the reach of at these machines. We also examine
the viability of models with an inverted mass hierarchy (IMH), where
third generation sfermions are by far lighter than those of the first
two generations. We find that a radiatively generated hierarchy is
considerably smaller than claimed in the literature. A larger hierarchy
is possible if it is assumed to be present at the GUT scale. We briefly
discuss phenomenological implications of these scenarios. The third
part is about some ongoing work about B_s -> mu mu and B_d -> tau tau
decays. Within the mSUGRA framework, we find that it may be possible to
probe the former at the Tevatron, and posssibly, the latter at B-factories.
We are also examining these decays in gauge-mediated SUSY breaking and
anomaly-mediated SUSY breaking scenarios, and will present results as
they are available.
|
| Feb. 4: | Top Quark Physics and Higgs Searches at the Tevatron Collider |
| Emanuela Barberis | |
| LBL
The particle physics adventure, during the period of
nearly one century, has witnessed the achievement of
numerous milestones and is now exciting as ever.
We have a model, the Standard Model of particle physics,
which succesfully predicts the fundamental
constituents of matter and their interactions in the energy regime in which we conduct our experiments. We know it cannot predict phenomena beyond the TeV scale and must therefore be subsumed by a more
fundamental theory at higher energy scales. The last of the found building blocks, the top quark, was discovered at Fermilab in 1995. Its mass and properties have profound implications on the validity and predictions of the Standard Model. I will review our current knowledge of the top quark, give prospects for future Tevatron measurements, and discuss how there measurements will influence our understanding of the Standard Model. Top quark properties relate to the undiscovered sector of the Standard Model, the Higgs field. The Higgs field in the Standard Model is responsible for the generation of all particle masses. I will describe the prospects for observing a Standard Model Higgs particle at the Tevatron.
|
| Feb. 11: | Search for Supersymmetry in Run II of the Tevatron |
| Yuri Gershtein | |
| Brown U.
The current model of the elementary particle world (the Standard Model) is now several decades old and still defies all experimental attempts to overthrow it. There are many reasons to believe however, that the SM is just an effective theory which is replaced at higher energies by a more general one. Supersymmetry is a very strong candidate for such a theory. Depending on exact manner in which the particular supersymmetric theory is constructed it can give rise to a variety of experimental signatures. Some, like jets and missing energy or multiple leptons were extensively looked for in Run I. I will discuss the prospects of SUSY discovery in Run II. Also, in the past few years a lot of attention were given to models which have heavy quasi-stable particles and/or tau leptons in the final state. Making a discovery in these final states requires novel approaches to hardware trigger and analysis techniques. I will describe these approaches and give an outlook of Run II possibilities.
|
| Feb. 18: | |
| Feb. 25: | Neutrino Oscillations with Super-Kamiokande and MINOS |
| Mark Messier | |
| Harvard
Since its announcement of evidence for neutrino oscillations, and hence non-zero neutrino mass, the Super-Kamiokande experiment has more than doubled the size of its data set. In this talk, I will review the current status of the evidence for neutrino oscillations focusing on the results from Super-Kamiokande. Looking beyond current results, I will discuss the capabilities of the MINOS long baseline experiment currently under construction. The MINOS experiment will pass an intense neutrino beam produced at the Fermilab main injector through two detectors separated by 735 km. Through a high statistics measurement of the neutrino energy spectra at the near and far locations MINOS will provide detailed information on the mechanism of muon neutrino disappearance and precise measurements of oscillation parameters.
|
| Mar. 4: | Preons or PDFs? And where is the Higgs? |
| Levan Babukhadia | |
| SUNY Stony Brook
I will describe the latest about quest for quark substructure
at the energy frontier at the Fermilab Tevatron in light of recent,
significantly extended inclusive jet production measurement with
the Run I DZero collider detector. It is the first time that the
Tevatron jets data start to play very important role in constraining
parton and especially gluon distribution functions (PDFs). It
appears that observed possible excess at high jet transverse momenta
might be accommodated by modified gluon PDF at moderate and high
fractions of parton momentum transfer. Recently released CTEQ and
MRST PDF sets are already incorporating these new jets data with
interesting and profound implications. The Tevatron Run II is ongoing. One of the main goals is to unveil the problem of electroweak symmetry breaking by perhaps discovering the elusive Higgs particle. I will briefly describe the fully digital, FPGA based Level 1 hardware track trigger to aid in selection of interesting events at very early stages of triggering and will describe prospects for searching for Higgs in Run II in general and with enhanced coupling to bottom quarks in particular.
|
| Mar. 11: | NO SEMINAR THIS WEEK |
| Spring Break | |
| Mar. 18: | Measurement of CP Violation in B Meson Decay |
| Erich Varnes | |
| Princeton U.
I will discuss the phenomenon of asymmetries under the combined transformation of charge conjugation and parity (CP), and explain the consequences of these asymmetries in particle physics and cosmology. I will then discuss the importance of measuring violations of CP symmetry in the B meson system, and describe the recent measurement of the CP-violation parameter sin2beta with the BaBar detector at SLAC, with a focus on how events are selected for the measurement.
|
| Mar. 25:
Special Colloquium |
The Inner Limits: Physics at the Smallest Distance Scales |
| Darien Wood | |
| Northeastern U.
Since the pioneering work of Rutherford, physicists have used energetic
particles to probe deeper and deeper into matter. The DZero experiment
exploits the highest energy accelerator in the world, the Tevatron, to
study collisions between protons and antiprotons. The laws of physics
are tested down to distance scales of less than 10^-18 m, and the most
massive fundamental particles yet discovered are observed and studied.
|
| Apr. 1: | |
| Apr. 8: | Supersymmetric Particle Production at Hadron Colliders |
| Tilman Plehn | |
| U. Wisconsin
Supersymmetry is probably the most attractive theoretical environment for physics beyond the electroweak scale. Hadron Colliders like the Tevatron and the LHC have great potential to confirm these ideas. A large number of production channels and decay chains can be explored. For several reasons these searches heavily rely on the theoretical knowledge of the production cross sections, including higher order corrections. I will give an introducion to the most relevant search channels including the effect of higher order SUSY-QCD predictions. Moreover, I will give a brief overview of the methods and challenges in these computations.
|
| Apr. 15: | Reopening the window for electroweak baryogenesis in cosmologies with non-standard Friedmann equation |
| Geraldine Servant | |
| U. of Chicago/Argonne
In this talk, I will start by reviewing the motivations and problematic of the theory of electroweak baryogenesis as well as the major serious constraints it implies on the particle physics side (especially on the Higgs mass). Our main point will then be to discuss and modify the standard assumption made on the thermal history of the universe. The value of the expansion rate of the universe at the time of the electroweak phase transition is a crucial ingredient since it controls the out-of-equilibrium condition needed from producing a stable baryon asymmetry. This out-of-equilibrium condition leads to the so-called "sphaleron bound". I will sketch the derivation of that bound and its translation into major particle physics constraints. I will mention previous attempts to evade that bound and will next focus on a specific form for the Friedmann equation (which gives the expansion rate of the universe) inspired by brane cosmology. I will show that such modification of cosmology turns out to affect positively the viability of electroweak baryogenesis with relaxed bounds on the Higgs mass for instance.
|
| Apr. 22: | |