A Fall 2010 external visiting committee described the Physics Department as “one of the top physics programs in the Nation” and “one of the most brilliant jewels of Williams College.” Another remarks, “It is not a coincidence that year after year Williams College is the top choice for a disproportionately large number of high school seniors who want to major in physics. The Department of Physics at Williams College offers one of the very best undergraduate programs in the country.”
Eighteen Physics and Astrophysics majors graduated in June. Four will start graduate work in science or math, three science research, two high school physics teaching, two work in alternative energy, two work on healthcare software. This proves again what good preparation these majors are for many professions.
The department continues to actively engage students in research. Last summer 18 students were on campus doing physics research with a similar number this summer. Eight seniors completed honors research projects.
Prof. Tucker-Smith gave a Faculty Lecture about the search for the Higgs at the LHC. Prof. Strauch gave two Sigma Xi Lectures about quantum entanglement. The rest of the Physics and Astronomy colloquium program was excellent this year, and included four alumni – Josh Cooperman ’05, Patty Liao ’09, Tim McConnochie ’98, and David Butts ‘06 – who presented their work and met with students to talk about the paths they’ve taken in their careers. We also co-hosted Gioia De Cari who performed her one-woman play “Truth Values” about women in science.
Professor and Chair Daniel Aalberts taught Introductory Mechanics (PHYS 131) to 72 students in the fall and Statistical Mechanics and Thermodynamics (PHYS 302) in the spring. In the Aalberts Lab, thesis student Julian Hess `13 enhanced an algorithm for RNA binding to include mean unfolding costs at the target while Joel Clemmer `12 developed measures for the information of RNA folds. Jeff Meng ‘11 returned to write a paper based on his thesis work modeling stretched loops related to small RNA-mRNA binding. Scientific Programmer Bill Jannen ’09 worked on an algorithm to cluster related RNA structures. Aalberts also collaborates with John Hunt (Columbia Univ) on methods to enhance gene expression. This summer, he will continue research with Julian Hess ’13 and develop his new course (PHYS 231T Facts of Life) with Olivia Uhlmann ’13.
During summer 2011 Professor Kevin Jones, along with Christina Knapp ’13 and David Kealhofer ’13, worked on a quantum optics experiment at the National Institute of Standards and Technology (NIST) in Gaithersburg, MD. The students were supported by a grant from NIST’s Summer Undergraduate Research Fellowship program and Jones was supported as a Guest Researcher by a different NIST grant. The research group which hosted their visit is headed by Dr. William Phillips (1997 Nobel Laureate). The Williams contingent worked closely with Dr. Paul Lett and other NIST scientists on an experiment to produce quantum states of light, i.e. light beams that have properties that cannot be produced by any classical optics device. David and Christina constructed a diode laser system for doing four-wave mixing (a non-linear optics process) in cesium vapor. By the end of the summer they were able to demonstrate a four-wave mixing signal, verifying that the laser systems that they had constructed had the necessary power and spectral properties for the project. Jones will be continuing this project in summer 2012.
Jones, with NIST coauthors, published a paper in the journal Optics Express reporting on the development of a source for a particular quantum state of light, “multi-spatial mode squeezed vacuum,” of potential interest for quantum imaging applications. Jones and colleagues are currently working on another manuscript, describing their development of a noiseless amplifier for optical images. It has long been appreciated that quantum states of light have interesting properties for image processing and information processing, but actually producing and manipulating these states has been a significant experimental challenge. Jones continues to collaborate with the NIST group on new projects in this area.
For the past year, Ward Lopes has been on sabbatical as part of his Assistant Professor Leave. During part of the time, he traveled to the University of Illinois to continue working on a collaboration he has with Paul Selvin’s lab. With the rest of his time, Ward has been at Williams continuing work on experiments and computations that had been started in his lab. Since the last report on Science, Ward has been coauthor on two published papers and he is currently writing two more.
During the 2011-12 academic year, Prof. Tiku Majumder continued his term as Director of the Science Center and Chair of the Science Executive committee. In his administrative role, he has supervised and supported faculty research funding, the student research program, and has focused on numerous facilities, development, and admissions projects which relate to the Science Center. He also taught Physics 301, Quantum Mechanics, and its associated advanced laboratory, to a large group of 21 students in the fall of 2011. He continued to pursue diode laser and atomic physics experiments in his research lab, teaming up with senior thesis students Anders (Andy) Schneider ’12 and Taryn Siegel ‘12, and current postdoc Dr. Gambhir Ranjit. Gambhir was hired with funds from Majumder’s $300,000 NSF grant, which also supports summer research students as well as the purchase of numerous new pieces of scientific equipment.
The Majumder lab continues to pursue very high precision measurements of atomic structure of the heavy metal elements thallium and indium. These measurements test state-of-the-art calculations of atomic structure in these multi-electron atoms, and are useful in providing ‘table-top’ tests of fundamental physics of the sort normally associated with elementary particle theory and high-energy accelerators. The two current experimental projects in the Majumder lab involve the use of various semiconductor diode laser systems and atomic sources of thallium (in heated vapor cells) and indium (in a high-vacuum atomic beam apparatus). Taryn Siegel ’12 completed her thesis this spring which involved setting up a two-laser (IR, UV) spectroscopy system to observe and measure two-step spectroscopy in thallium atoms contained in a 600 oC quartz thallium cell. Taryn was able to lock the UV laser used for the first-step excitation, and scan the IR laser to obtain initial hyperfine spectra for the second-step excitation.
Andy Schneider ’12 also completed his thesis work this spring, following up on the development work of his predecessor in the lab, Tony Lorenzo ’11. Andy worked to optimize the indium atomic beam system and the 410 nm laser frequency-modulation spectroscopy setup, and was able to collect and analyze our first indium Stark shift data by applying 10-12 kV/cm electric fields to the atomic beam. Andy is headed to Houston to begin a two-year high school teaching position prior to attending graduate school in physics. Tony Lorenzo spent this post-graduate year working in the Williams physics department as a lab instructor, and is now headed to the Optical Sciences Ph.D. program at U. Arizona.
In June, Prof. Majumder and Dr. Ranjit attended the APS Division of Atomic, Molecular, and Optical physics meeting in Anaheim, CA, presenting two well-received posters, which presented the work of both thesis students this year. Incoming thesis students David Kealhofer ’13 and Nathan Schine ’13 will have the task of collecting and analyzing substantial amounts of data from both the beam and cell experiments. The group expects to complete and publish the results of both measurements this year.
Over the past year, Visiting Assistant Professor Michael Seifert has continued his research into possible violations of Lorentz symmetry. Lorentz symmetry is thought to be a fundamental symmetry of nature, describing how space and time are related to each other; Seifert’s research studies how a breaking of this symmetry could be mathematically modeled and experimentally detected. His current projects deal primarily with the consequences of Lorentz symmetry violation in the context of gravitational phenomena, and with a class of solutions called “topological defects” that can arise when symmetries of nature are broken. In the summer of 2012, Seifert will act as a summer research supervisor for Kamuela Lau ’14 and Brandon Ling ’15, who will be conducting research into the properties of topological defect solutions in the context of Lorentz symmetry violation.
During the 2011-12 academic year, Seifert taught Electromagnetic Theory (PHYS 411), an advanced tutorial class, and Electromagnetism and the Structure of Matter (PHYS 132), the second semester of a two-semester introductory sequence. Seifert also began to develop a new Winter Study course, Quantum Mechanics and the Nature of Reality, to be offered in January 2013
Professor Jefferson Strait and his students have built and are studying an optical fiber laser that produces pulses of light about one picosecond long. Unlike most lasers, which use mirrors to confine light to the laser cavity, an optical fiber laser uses a loop of fiber as its cavity. A section of fiber doped with erbium acts as the gain medium. It lases at 1.55 microns, conveniently the same wavelength at which optical fiber is most transparent and therefore most suitable for telecommunications. This laser functions as a test bed for short pulses of light propagating in fiber. Joseph Iafrate ’14 will work with Strait during the summer of 2012 extending this project.
Strait serves as pre-engineering advisor, department webmaster, and College Marshal, the faculty member responsible for coordinating the Convocation and Commencement ceremonies.
Assistant Professor Frederick Strauch was on leave during the 2011-2012 year. He continued his theoretical work in superconducting quantum circuits, quantum algorithms, and other applications to quantum information processing, in collaboration with Kurt Jacobs at the University of Massachusetts Boston and Ray Simmonds of the National Institute of Standards and Technology in Boulder, CO, supported by a continuing grant of $233,186 from the National Science Foundation.
During the year Strauch consulted (with MITRE corporation) for the Intelligence Advanced Research Projects Activity (IARPA) program for Quantum Computer Science. This multi-year project poses several challenge problems to determine the resource requirements to run quantum algorithms on potential physical implementations. Strauch’s involvement over the past year includes the preparation of specification for a superconducting quantum computer, running a small technical workshop in December 2011 at the University of Southern California, and helping to organize and run a general workshop for the program in Minneapolis in May 2012.
Strauch also engaged in a number of trips to conferences, workshop, and research institutions. His first trip, in November 2011, was to Valencia, Spain to give an invited talk for the International Workshop on Theoretical Aspects of the Discrete Time Quantum Walk. Strauch returned to deliver two Sigma Xi lectures to the Williams community on his research in entanglement in superconducting circuits, an opportunity he enjoyed immensely. He subsequently traveled to the annual meeting of SQuInt (Southwest Quantum Information and Technology network) in Albuquerque, NM and visited NIST in Boulder, CO in February 2012, presenting a talk on his research in controlling superconducting resonators. He finished his travels by returning to Boston for a contributed talk to the March Meeting of the American Physical Society.
Strauch continues to publish in Physical Review Letters, Physical Review A (with Douglas Onyango ’11), and hopes to finish several manuscripts before returning to the classroom in the Fall. During the summer of 2012, he will be working with Nathan Saffold ’14, Roshan Sharma ’13, and Qiao Zhang ’13.
Associate Professor David Tucker-Smith continued his research in theoretical particle physics. With his students and colleagues, Tucker-Smith studies how models of new physics can be tested at the Large Hadron Collider (LHC) and other experiments. In the summer of 2011, Tucker-Smith worked with Dylan Gilbert ’13 and Margot Robinson ’12 on strategies for searching for a new gauge boson that couples preferentially to bottom quarks, and with Murat Kologlu ’12 he investigated new physics explanations of the anomalously large top forward-backward asymmetry measured at the Tevatron. Murat and Margot continued their research during the academic year for their senior honors theses. Murat will begin Caltech’s physics PhD program in the fall, while Margot will pursue an M.P.H at the University of Washington. In the coming year Dylan Gilbert ’13 will continue on as a thesis student under Tucker-Smith’s supervision, along with Alice Sady ’13, who will return from studying abroad in Geneva and doing research at CERN.
In the fall semester of 2011 Tucker-Smith taught Newton, Einstein, and Beyond (PHYS 107), a course intended for non-scientists, and in the spring semester he taught Mathematical Methods for Scientists (PHYS 210), and an introduction to Einstein’s general relativity, Gravity (PHYS 418). In March Tucker-Smith participated in a workshop on Monte Carlo tools for new physics at the LHC, at Cornell University.
Professor Bill Wootters worked this year with thesis student Tori Borish ’12 on the “ubit” model of quantum mechanics. Normally quantum mechanics is expressed in terms of complex numbers; the ubit model provides a way of re-expressing the theory using only real numbers. The resulting difference in perspective suggests certain slight modifications of standard quantum theory, some of which had been studied numerically by Antoniya Aleksandrova ’11. Tori’s main objective, on which she made excellent progress, was to understand these effects analytically by means of perturbation theory.
In the summer of 2011, in addition to pursuing the ubit project Wootters worked with Roshan Sharma ’13 on the problem of finding and characterizing “minimum uncertainty states” in the quantum mechanics of discrete systems, an investigation that was continued by Ilya Amburg ’14 during the academic year. During the winter study period of 2012, Christina Knapp ’13 began a project on quantum entanglement and composite bosons that she plans to continue for her senior thesis. That project extends a line of research initially explored a few years ago by Chris Chudzicki ’10 and Jimi Oke ’10.
Wootters gave talks on the ubit model at a few institutions, including the Institute of Mathematical Sciences in Chennai, India, which he visited during spring break. He also gave an invited talk at the American Physical Society’s March meeting in Boston as part of a session on teaching quantum information science at liberal arts colleges
Class of 1960 Scholars in Physics
Victoria F. Borish
Julian M. Hess
Margaret G. Robinson
Joel T. Clemmer
Anders E. Schneider
Taryn R. Siegel
[Colloquia are held jointly with the Astronomy Department.]
Joshua Cooperman ’05, University of California, Davis
“Causal Dynamical Triangulations: How to Simulate Quantum Gravity on Your Laptop ”
Patty Liao ’09, University of Michigan
“Physics-Engineering Continuum: Focus on Energy Applications”
Louisa Gilder, author of The Age of Entanglement
“The Early History of Entanglement: EPR Before 1935”
Daniel Reich, Johns Hopkins University
“Probing Sub-Cellular Force Dynamics and Soft Matter Using Magnetic Nanowires ”
Eric Dufresne, Yale University
“Electrostatics Meets Entropy”
Zosia Krusberg, Vassar College
“The Phenomenology of Maverick Dark Matter”
Kourosh Zarringhalam, Boston College
“Recent Results on the Thermodynamics and Kinetics of RNA Secondary Structure ”
Leon Golub, Smithsonian Astrophysical Observatory
“A New View of the Solar Corona ”
Timothy McConnochie ’98, NASA Goddard Space Flight Center
“Observing the Dynamics of the Mars Polar Vortex ”
Debra Rolison, Naval Research Lab
“Integrating the Multifunction Necessary for Electrochemical Power into Energy and Size-Scalable Ultraporous Nanoarchitectures ”
Anne Goodsell, Middlebury College
“Exciting Physics with Excited Atoms ”
Thomas Baumgarte, Bowdoin College
“Binary Black Hole Mergers ”
David Butts ’06, Draper Laboratory
“Inertial Sensing with Cold Atoms ”
OTHER ON CAMPUS PRESENTATIONS
“Somewhere over the RNAbow”
Summer Science Lunch Talk, 2011
Bronfman Faculty Lunch Talk, April 10, 2012
“Entanglement: Schrodinger’s Quirky Quantum Conundrum”
Sigma Xi Lecture, Part I, November 17, 2011
“Entanglement in Superconducting Quantum Circuits”
Sigma Xi Lecture, Part II, November 18, 2011
“The Latest From the LHC”
Bronfman faculty lunch talk, October 21, 2011
“Searching for the Higgs at the LHC”
Faculty Lecture Series, February 23, 2012
Daniel P. Aalberts
“RNAbows: an intuitive tool for RNA structure visualization”
poster presentation at the RNA Symposium, U Albany, 2011
(with Bill Jannen ’09)
Daniel P. Aalberts
“Computing Effective Free Energy to Bind an Oligo to an mRNA
the Bindigo-MFT algorithm poster presentation at the RNA Symposium, U Albany, 2011
(with Julian Hess ’13)
Daniel P. Aalberts
“Base Pairing Probability and Composition Asymmety in RNA”
poster presentation at the RNA Symposium, U Albany, 2011
(with Joel Clemmer ‘12)
Daniel P. Aalberts
“Intuitive ways of visualizing RNA folds and landscapes”
Joint Physics and Biology Colloquium, Boston College
“Precise Atomic Beam Measurement of the Stark Shift within the 5P1/2 à 6S1/2 Transition In Using FM Spectroscopy ” poster presentation at the APS Division of Atomic, Molecular, and Optical Physics Meeting, Anaheim, CA, June 4 – June 9, 2012
(with Gambhir Ranjit, A. Schneider ’12, and N. Schine ‘13)
“Measuring Hyperfine Structure and Isotope Shift in the Thallium 7S1/2 à 7P1/2 Transition Using Two-Color Spectroscopy” poster presentation at the APS Division of Atomic, Molecular, and Optical Physics Meeting, Anaheim, CA, June 4 – June 9, 2012
(with Gambhir Ranjit, and T. Siegel ’12)
“Heavy Metal, Cheap Lasers and Tests of Fundamental Physics ”
Bowdoin college, invited department colloquium
“Lorentz Symmetry and How to Break It ”
Hamilton College, invited department colloquium
“Quantum Walks in Discrete and Continuous Time ”
International Workshop on Theoretical Aspects of the Discrete Time Quatum Walk
“Entanglement State Synthesis for Superconducting Resonator Qudits ”
Southwest Quantum Information and Technology Workshop
“Keeping It Real: Quantum Mechanics without Complex Numbers”
Department of Physics, University at Albany
“Theoretical Research Fostered by an Undergraduate Environment”
APS March Meeting, Boston
“Qualitative Distinctions between Standard Quantum Theory and Its Real-Vector-Space Analogue”
Institute of Mathematical Sciences, Chennai, India
“Quantum Mechanics as a Real Vector-Space Theory with a Universal Auxilieary Rebit”
Institute of Mathematica Sciences, Chennai, India
“The Ubit Model in Real-Vector-Space Quantum Theory”
Perimeter Institute, Waterloo, Ontario, Canada
POSTGRADUATE PLANS OF DEPARTMENT MAJORS
|Victoria F. Borish||Research Assistant in Anton Zeilinger’s Group, University of Vienna, Austria|
|Joel T. Clemmer||MGH Global Health (1yr, South Sudan Clinical/Organizational – Blood Bank|
|Thomas Crawford||Math PhD at Boston College|
|Maia D. Dickinson||Publishing in NYC or museum research in Anchorage|
|Richard D. Fusco||Alternative Energy company outside of NYC|
|Marni L. Jacobs||Teaching in Dorchester, Med at Tufts|
|Stephanie A. Jensen||Professional consulting for various firms|
|Murat Kologlu||Caltech PhD (Theoretical Partical Physics)|
|Peter S. Mertz||E4Sciences (Geophysics consulting firm in CT)|
|Benjamin M. Oliva||unknown|
|Margaret G. Robinson||Institute for Health metrics and Evaluation (2yr postbac Seattle)|
|Michael S. Ryan||Booz-Allen Hamilton (tech consulting for DoD in DC)|
|Takuto Sato||Intersystems (Boston, software, hospital databases)|
|Anders E. Schneider||Teaching 11th Grade Physics in Houston (Teach for America)|
|Liyang Zhang||Mathematical Physics PhD at Yale|
The Ubit Real-Vector-Space Model: Deviations from Standard Quantum Theory
Victoria F. Borish
Quantum mechanics (the framework for much of modern physics) has always been described by the complex numbers; however there are reasons to consider describing it with purely real numbers instead. In my thesis, I investigate a specific model of real-vector quantum theory and try to explain some effects I see that deviate from standard quantum theory.
Information of RNA Folding
Joel T. Clemmer
We computationally studied the information already known about how a particular sequence will fold and with experimental methods in mind, quantified the information gained for particular measurements.
Efficiently Estimating Net Free Energy to Bind Oligomeric RNAs to mRna
Julian M. Hess
In this thesis, we create a method to improve the accuracy of algorithms that predict RNA-RNA binding configurations.
An Effective SU(2)’ for Top Forward-Backward Asymmetry
We propose a theoretically consistent extension of the Standard Model to explain the anomalous top quark forward-backward asymmetry observed at the Tevatron. Our model is shown to better explain the observed asymmetry while producing reasonable top production phenomenology and meeting dijet and other constraints.
Searching for a b-friendly Z’ Boson at the LHC
Margaret G. Robinson
The search for new phenomena not predicted by the Standard Model (SM) of particle physics is a primary goal of the Large Hedron Collider (LHC). This thesis examines the phenomenology of a neutral gauge boson, a $Z’$, that couples predominantly to right-handed SM bottom quarks.
Measuring the stark Shift in the SP1/2 à 651/2 410 nm Transition in Indium
Anders E. Schneider
An investigation of the effect of a strong electric field on the energy level structure of indium with the goal of determining its atomic polarizability.
Measurement of the Hyperfine Splitting and Isotope Shift for the 751/2 à 7P1/2 Transition in Thalium Using Two-Step Excitation Laser Spectroscopy
Taryn R. Siegel
We use two lasers to excite the valence electrons of thalium in order to measure subtle features of thalium’s level structure very precisely.
Loop Entropy Assists Tertiary Order: Loopy Stabilization of Stacking Motifs
Daniel P. Aalberts
Entropy, 13, 1958-1966 (2011)
The free energy of an RNA fold is a combination of favorable base pairing and stacking interactions competing with entropic costs of forming loops. Here we show how loop entropy, surprisingly, can promote tertiary order. A general formula for the free energy of forming multibranch and other RNA loops is derived with a polymer-physics based theory. We also derive a formula for the free energy of coaxial stacking in the context of a loop. Simulations support the analytic formulas. The effects of stacking of unpaired bases are also studied with simulations.
Multi-spatial-mode Single-Beam Quadrature Squeezed States of Light From Four-Wave Mixing in Hot Rubidium Vapor
Kevin M. Jones, McElfresh, and others
Optics Express, 19, 21358 (2011)
We present experimental results on the generation of multispatial-mode, single-beam, quadrature squeezed light using four-wave mixing in hot Rb vapor. Squeezing and phase-sensitive deamplification are observed over a range of powers and detunings near the 85Rb D1 atomic transition. We observe -3 dB of vacuum quadrature squeezing, comparable to the best single-spatial mode results previously reported using atomic vapors, however, produced here in multiple spatial modes. We confirm that the squeezing is present in more than one transverse mode by studying the spatial distribution of the noise properties of the field.
Two-Photon 3D FIONA of Aqueous Individual Quantum Dots
Ruobing Zhang, Eli Rothenberg, Gilbert Fruhwirth, Paul Simonson, Fangfu Ye, Ido Golding, Tony Ng, Ward Lopes, Paul Selvin
Nano Letters, 11, 4074 (2011)
We report the first two-photon (2P) microscopy of individual quantum dots (QDs) in an aqueous environment with both widefield and point-scan excitations at nanometer accuracy. Thiol-containing reductants suppress QD blinking and enable measurement of the 36 nm step size of individual Myosin V motors in vitro. We localize QDs with an accuracy of 2–3 nm in all three dimensions by using a 9 × 9 matrix excitation hologram and an array detector, which also increases the 3D scan imaging rate by 80-fold. With this 3D microscopy we validate the LamB receptor distribution on E. coli and the endocytosis of EGF-receptors in breast cancer cells.
Chemical Surface Nanopatterning Using Block Copolymer Templates
N.A. Yufa, S.L. Frank, S.J. Rosenthal, Seth B. Darling, W.A. Lopes, and S. J. Sibener
Materials Chemistry and Physics, 125, 382 (2011)
Thin-film poly(styrene-block-methyl methacrylate) diblock copolymer (PS-b-PMMA) is used to create chemically patterned surfaces via metal deposition combined with self-assembled monolayers (SAMs) and UV exposure. We use this method to produce surfaces that are chemically striped on the scale of a few tens of nanometers. Atomic force and transmission electron microscopies are used to verify the spatially localized organization of materials, and contact angle measurements confirm the chemical tunability of these scaffolds. These surfaces may be used for arraying nanoscale objects, such as nanoparticles or biological species, or for electronic, magnetic memory or photovoltaic applications.
Ultraeffiecient Cooling of Resonators: Beating Sideband Cooling with Quantum Control
X. Wang, S. Vinjanampathy, F.W. Strauch, and K. Jacobs
Phys.Rev. Letters, 107, 177204 (2011)
The present state of the art in cooling mechanical resonators is a version of sideband cooling. Here we present a method that uses the same configuration as sideband cooling—coupling the resonator to be cooled to a second microwave (or optical) auxiliary resonator—but will cool significantly colder. This is achieved by varying the strength of the coupling between the two resonators over a time on the order of the period of the mechanical resonator. As part of our analysis, we also obtain a method for fast, high-fidelity quantum information transfer between resonators.
Quantum Logic Gates for Superconducting Resonator Qudits
Phys.Rev.A ,84, 052313 (2011)
We study quantum information processing using superpositions of Fock states in superconducting resonators as quantum d-level systems (qudits). A universal set of single and coupled logic gates is theoretically proposed for resonators coupled by superconducting circuits of Josephson junctions. These gates use experimentally demonstrated interactions and provide an attractive route to quantum information processing using harmonic oscillator modes.
Entangled-State Synthesis for Superconducting Resonators
F.W. Strauch, D. Onyango, K. Jacobs, and R.W. Simmonds
Physical Rev.A, 85, 022335 (2012)
We present a theoretical analysis of methods to synthesize entangled states of two superconducting resonators. These methods use experimentally demonstrated interactions of resonators with artificial atoms and offer efficient routes to generate nonclassical states. We analyze physical implementations, energy level structure, and the effects of decoherence through detailed dynamical simulations.
Singlet-Doublet Dark Matter
Timothy Cohen, Jonh Kearney, Aaron Pierce and David Tucker-Smith
Phys.Rev.D, 85, 075003 (2012)
In light of recent data from direct detection experiments and the Large Hadron Collider, we explore models of dark matter in which an SU(2) doublet is mixed with a Standard Model singlet. We impose a thermal history. If the new particles are fermions, this model is already constrained due to null results from XENON100. We comment on remaining regions of parameter space and assess prospects for future discovery. We do the same for the model where the new particles are scalars, which at present is less constrained. Much of the remaining parameter space for both models will be probed by the next generation of direct detection experiments. For the fermion model, DeepCore may also play an important role.
Higgs Friends and Counterfeits at Hadron Colliders
Patrick J. Fox, David Tucker-Smith and Neal Weiner
JHEP., 127, 1106 (2011)
We consider the possibility of “Higgs counterfeits” – scalars that can be produced with cross sections comparable to the SM Higgs, and which decay with identical relative observable branching ratios, but which are nonetheless not responsible for electroweak symmetry breaking. We also consider a related scenario involving “Higgs friends,” fields similarly produced through gg fusion processes, which would be discovered through diboson channels WW, ZZ, γγ, or even γZ, potentially with larger cross sections times branching ratios than for the Higgs. The discovery of either a Higgs friend or a Higgs counterfeit, rather than directly pointing towards the origin of the weak scale, would indicate the presence of new colored fields necessary for the sizable production cross section (and possibly new colorless but electroweakly charged states as well, in the case of the diboson decays of a Higgs friend). These particles could easily be confused for an ordinary Higgs, perhaps with an additional generation to explain the different cross section, and we emphasize the importance of vector boson fusion as a channel to distinguish a Higgs counterfeit from a true Higgs. Such fields would naturally be expected in scenarios with “effective Z’s,” where heavy states charged under the SM produce effective charges for SM fields under a new gauge force. We discuss the prospects for discovery of Higgs counterfeits, Higgs friends, and associated charged fields at the LHC.
An Effective Z’
Patrick J. Fox, Jia Liu, David Tucker-Smith and Neal Winter
Phys.Rev.D, 84, 115006 (2011)
We describe a method to couple Z’ gauge bosons to the standard model (SM), without charging the SM fields under the U(1)’, but instead through effective higher dimension operators. This method allows complete control over the tree-level couplings of the Z’ and does not require altering the structure of any of the SM couplings, nor does it contain anomalies or require introduction of fields in non-standard SM representations. Moreover, such interactions arise from simple renormalizable extensions of the SM – the addition of vector-like matter that mixes with SM fermions when the U(1)’ is broken. We apply effective Z’ models as explanations of various recent anomalies: the D0 same-sign dimuon asymmetry, the CDF W+dijet excess and the CDF top forward-backward asymmetry. In the case of the W+dijet excess we also discuss several complementary analyses that may shed light on the nature of the discrepancy. We consider the possibility of non-Abelian groups, and discuss implications for the phenomenology of dark matter as well.
Limited Holism and Real-Vector-Space Quantum Theory
Lucien Hardy and William K. Wootters,
Found.Phys., 42, 454-473 (2012)
Quantum theory has the property of “local tomography”: the state of any composite system can be reconstructed from the statistics of measurements on the individual components. In this respect the holism of quantum theory is limited. We consider in this paper a class of theories more holistic than quantum theory in that they are constrained only by “bilocal tomography”: the state of any composite system is determined by the statistics of measurements on pairs of components. Under a few auxiliary assumptions, we derive certain general features of such theories. In particular, we show how the number of state parameters can depend on the number of perfectly distinguishable states. We also show that real-vector-space quantum theory, while not locally tomographic, is bilocally tomographic.