arXiv subjects

David Toback

Publications and source records attributed to David Toback.

15 recordsLinked to original sources

arXiv2022

The level-1 trigger for the SuperCDMS experiment at SNOLAB

The SuperCDMS SNOLAB dark matter search experiment aims to be sensitive to energy depositions down to O(1 eV). This imposes requirements on the resolution, signal efficiency, and noise rejection of the trigger system. To accomplish this, the SuperCDMS level-1 trigger system is implemented in an FPGA on a custom PCB. A time-domain optimal filter algorithm realized as a finite impulse response filter provides a baseline resolution of 0.38 times the standard deviation of the noise, $\sigma_n$, and a 99.9% trigger efficiency for signal amplitudes of 1.1 $\sigma_n$ in typical noise conditions. Embedded in a modular architecture, flexible trigger logic enables reliable triggering and vetoing in a dead-time-free manner for a variety of purposes and run conditions. The trigger architecture and performance are detailed in this article.

physics.ins-det↗

arXiv2018

Energy Loss Due to Defect Formation from $^{206}$Pb Recoils in SuperCDMS Germanium Detectors

The Super Cryogenic Dark Matter Search experiment (SuperCDMS) at the Soudan Underground Laboratory studied energy loss associated with Frenkel defect formation in germanium crystals at mK temperatures using in situ $^{210}$Pb sources. We examine the spectrum of $^{206}$Pb nuclear recoils near its expected 103 keV endpoint energy and determine an energy loss of $\left(6.08\pm0.18\right)$ %, which we attribute to defect formation. From this result and using TRIM simulations, we extract the first experimentally determined average displacement threshold energy of $\left(19.7^{+0.6}_{-0.5}\right)$ eV for germanium. This has implications for the analysis thresholds of future germanium-based dark matter searches.

physics.ins-det↗

arXiv2015

Extrapolation Technique Pitfalls in Asymmetry Measurements at Colliders

Asymmetry measurements are common in collider experiments and can sensitively probe particle properties. Typically, data can only be measured in a finite region covered by the detector, so an extrapolation from the visible asymmetry to the inclusive asymmetry is necessary. Often a constant multiplicative factor is more than adequate for the extrapolation and this factor can be readily determined using simulation methods. However, there is a potential, avoidable pitfall involved in the determination of this factor when the asymmetry in the simulated data sample is small. We find that to obtain a reliable estimate of the extrapolation factor, the number of simulated events required rises as the inverse square of the simulated asymmetry; this can mean that an unexpectedly large sample size is required when determining its value.

hep-ex↗

arXiv2014

Searches for New Particles and Interactions

We present a summary of results for searches for new particles and interactions at the Fermilab Tevatron collider by the CDF and the D0 experiments. These include results from Run I as well as Run II for the time period up to July 2014. We focus on searches for supersymmetry, as well as other models of new physics such as new fermions and bosons, various models of excited fermions, leptoquarks, technicolor, hidden-valley model particles, long-lived particles, extra dimensions, dark matter particles, and signature-based searches.

hep-ex↗

arXiv2014

Review of Physics Results from the Tevatron

We present a comprehensive review of the physics results obtained by the CDF and D0 collaborations up to summer 2014, with emphasis on those achieved in the Run II of the Tevatron collider which delivered a total integrated luminosity of ~10 fb-1 at sqrt{s}=1.96 TeV. The results are presented in six main physics topics: QCD, Heavy Flavor, Electroweak, Top quark, Higgs boson and searches for New Particles and Interactions. The characteristics of the accelerator, detectors, and the techniques used to achieve these results are also briefly summarized.

hep-ex↗

arXiv2014

On the Forward-Backward Asymmetry of Leptonic Decays of $t\bar{t}$ at the Fermilab Tevatron

We report on a study of the measurement techniques used to determine the leptonic forward-backward asymmetry of top anti-top quark pairs in Tevatron experiments with a proton anti-proton initial state. Recently it was shown that a fit of the differential asymmetry as a function of $q_{l}η_{l}$ (where $q_{l}$ is the charge of the lepton from the cascade decay of the top quarks and $η_{l}$ is the final pseudorapidity of the lepton in the detector frame) to a hyperbolic tangent function can be used to extrapolate to the full leptonic asymmetry. We find this empirical method to well reproduce the results from current experiments, and present arguments as to why this is the case. We also introduce two more models, based on Gaussian functions, that better model the $q_{l}η_{l}$ distribution. With our better understanding, we find that the asymmetry is mainly determined by the shift of the mean of the $q_{l}η_{l}$ distribution, the main contribution to the inclusive asymmetry comes from the region around $|q_{l}η_{l}| = 1$, and the extrapolation from the detector-covered region to the inclusive asymmetry is stable via a multiplicative scale factor, giving us confidence in the previously reported experimental results.

hep-ph↗

arXiv2013

Prospects for measuring the mass of heavy, long-lived neutral particles that decay to photons

We describe a novel way to measure the mass of heavy, long-lived neutral particles that decay to photons using collider experiments. We focus on a Light Neutralino and Gravitino model in a Gauge Mediated Supersymmetry Breaking scenario where the neutralino has a long-lifetime (O(ns)) as it is not excluded by current experiments. To illustrate our method and give sensitivity estimates we use recent CDF results and a production mechanism where sparticles are produced via $ϕ_{i} \rightarrow \widetildeχ^{1}_{0} \widetildeχ^{1}_{0} \rightarrow (γ\widetilde{G})(γ\widetilde{G})$ in which $ϕ_{i}$ indicates a neutral scalar boson, $\widetildeχ^{1}_{0}$ is the lightest neutralino and $\widetilde{G}$ is the gravitino, as a full set of background shapes and rates are available. Events can be observed in the exclusive photon plus Missing $E_{T}$ final state where one photon arrives at the detector with a delayed time of arrival. Surprisingly, a simple measurement of the slope of the delayed-time distribution with the full CDF dataset is largely insensitive to all but the $\widetildeχ^{1}_{0}$ mass and allows for the possibility of determining its mass to approximately 25% of itself.

hep-ph↗

arXiv2011

Prospects of Searches for Gauge Mediated Supersymmetry with h^0 -> {\chi}_1^0 {\chi}_1^0 production in the Time-Delayed Photon + MET Final State at the Tevatron

We propose a search for direct production and decay of the lightest supersymmetric Higgs boson to two neutralinos in gauge mediated models at the Fermilab Tevatron. We focus on the final state where each neutralino decays to photon and light gravitino with a lifetime of order O(ns). In the detector this will show up as a photon with a time-delayed signature and missing E_T. We estimate that using the photon timing system at CDF, and the full 10/fb data sample, that the sensitivity can be within a factor of three in some regions of parameter space for direct production of the Higgs.

hep-ph↗

arXiv2008

Determining the Dark Matter Relic Density in the Minimal Supergravity Stau-Neutralino Coannihilation Region at the Large Hadron Collider

We examine the stau-neutralino coannihilation (CA) mechanism of the early universe. We use the minimal supergravity (mSUGRA) model and show that from measurements at the Large Hadron Collider one can predict the dark matter relic density with an uncertainty of 6% with 30 fb-1 of data, which is comparable to the direct measurement by Wilkinson Microwave Anisotropy Probe. This is done by measuring four mSUGRA parameters m0, m1/2, A0 and tan(beta) without requiring direct measurements of the top squark and bottom squark masses. We also provide precision measurements of the gaugino, squark, and lighter stau masses in this CA region without assuming gaugino universality.

hep-ph↗

arXiv2007

Cosmology and Dark Matter at the LHC

We examine the question of whether neutralinos produced at the LHC can be shown to be the particles making up the astronomically observed dark matter. If the WIMP alllowed region lies in the SUGRA coannihilation region, then a strong signal for this would be the unexpected near degeneracy of the stau and neutralino i.e., a mass difference \Delta M\simeq (5-15) GeV. For the mSUGRA model we show such a small mass difference can be measured at the LHC using the signal 3\tau+jet+E_T^{\rm miss}. Two observables, opposite sign minus like sign pairs and the peak of the \tau\tau mass distribution allows the simultaneous determination of \Delta M to 15% and the gluino mass M_{\tilde g} to be 6% at the benchmark point of M_{\tilde g}=850 GeV, A_0=0, \mu>0 with 30 fb^{-1}. With 10 fb^{-1}, \Delta M can be determined to 22% and one can probe the parameter space up to m_{1/2}=700 GeV with 100 fb^{-1}.

hep-ph↗

arXiv2006

Detection of SUSY in the Stau-Neutralino Coannihilation Region at the LHC

We study the feasibility of detecting the stau neutralino (stau_1-neutralino_1)coannihilation region at the LHC using tau leptons. The signal is characterized by multiple low energy tau leptons from neutralino_2-->tau stau_1-->tau tau neutralino_1 decays, where the stau_1 and neutralino_1 mass difference (Delta M) is constrained to be 5-15 GeV by current experimental bounds including the bound on the amount of neutralino cold dark matter. Within the framework of minimal supergravity models, we show that if hadronically decaying tau's can be identified with 50% efficiency for visible pt >20 GeV the observation of such signals is possible in the final state of two tau leptons plus large missing energy and two jets. With a gluino mass of 830 GeV the signal can be observed with as few as 3-10 fb^-1 of data (depending on the size of Delta M). Using a mass measurement of the tau pairs with 10 fb^-1 we can determine dM with a statistical uncertainty of 12% for Delta M = 10 GeV and an additional systematic uncertainty of 14% if the gluino mass has an uncertainty of 5%.

hep-ph↗

arXiv2004

Run II Searches for Supersymmetry

In these proceedings, we present all of the Run II results in the search for Supersymmetry from the Tevatron. At the time of presentation ~200 pb-1 of Run II data had been analyzed for the presence of new physics. We summarize searches for CHAMPS, Squarks and Gluinos in the jets+Missing Transverse Energy (MET) final state, multiple dilepton final state analyses including B_s=>mumu, RPV Sneutrinos and Chargino/Neutralino production, and conclude with GMSB searches in the two photon + Met final state. While there is no evidence of new physics, we do note some interesting events and modest excesses for future reference as more data comes in. In many cases, the limits presented are the worlds first or most stringent.

hep-ex↗

arXiv2004

New Pedagogy for Using Internet-Based Teaching Tools in Physics Course

Acquiring the mathematical, conceptual, and problem-solving skills required in university-level physics courses is hard work, and the average student often lacks the knowledge and study skills they need to succeed in the introductory courses. Here we propose a new pedagogical model and a straight-forwardly reproducible set of internet-based testing tools. Our work to address some of the most important student deficiencies is based on three fundamental principles: balancing skill level and challenge, providing clear goals and feedback at every stage, and allowing repetition without penalty. Our tools include an Automated Mathematics Evaluation System (AMES), a Computerized Homework Assignment Grading System (CHAGS), and a set of after-homework quizzes and mini-practice exams (QUizzes Intended to Consolidate Knowledge, or QUICK). We describe how these tools are incorporated into the course, and present some preliminary results on their effectiveness.

physics.ed-ph↗

arXiv2000

New Phenomena II: Recent Results from the Fermilab Tevatron

The CDF and DØcollaborations continue to search for new physics using more than 100~pb$^{-1}$ of \xxbar{p} collisions at $\sqrt{s}=1.8$ TeV collected at the Fermilab Tevatron. We present recent results from both experiments on R-parity violating Supersymmetry and $Z'$/Technicolor production with $ee$ and \xxbar{t} final states. In addition we introduce Sherlock, a new quasi-model-independent search strategy.

hep-ex↗

arXiv1998

CDF Searches for New Phenomena

We present results of recent searches for new physics using the CDF detector at the Fermilab Tevatron. Presented are searches for Higgs -> gammagamma, as well as more general searches in gammagamma + X where X is missing Et, jets, charged leptons, b-quarks or extra photons. The CDF eegammagamma-mett candidate event is discussed along with estimates of the expected rates in the Standard Model. Other searches for SUSY, Higgs and Technicolor look for particles which decay to vector bosons and b-quarks.

hep-ex↗