Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “CDF”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 847 records · Page 47
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

Searches for Low Mass Higgs Boson at the Tevatron

We present the result of the searches for a low mass Standard Model Higgs boson performed at the Tevatron p{bar p} collider ({radical}s = 1.96 TeV) by the CDF and D0 experiments with an integrated luminosity of up to 8.5 fb{sup -1}. Individual searches are discussed and classified according to their sensitivity. Primary channels rely on the associate production with a vector boson (WH or ZH) and the H {yields} b{bar b} decay channel (favored for M{sub H} {approx}< 135 GeV/c{sup 2}). Event selection is based on the leptonic decay of the vector boson and the identification of b-hadron enriched jets. Each individual channel is sensitive, for M{sub H} = 115 GeV/c{sup 2}, to less than 5 times the SM expected cross section and the most sensitive channels can exclude a production cross section of 2.3 x {sigma}{sub H}{sup SM}. Secondary channels rely on a variety of final states. Although they are from 2 to 5 times less sensitive than any primary channel, they contribute to the Tevatron combination and, in some cases, they pose strong constrains on exotic Higgs boson models.

43 PARTICLE ACCELERATORS↗
DOE OSTI2011

Legacy limits and hints of New Physics at the Tevatron

This paper reviews results of beyond-the-standard model searches at the Tevatron presented in a plenary talk at the Europhysics Conference on High Energy Physics (EPS-HEP) in Grenoble. Here I present a selection of results from the CDF and D0 experiments that were shown at the conference during the parallel sessions. Much more is available and can be found at the experiment's web pages. This proceeding essentially focuses on searches in the dilepton, diboson, and t{bar t} final states. Throughout the paper, hints of new physics observed at the Tevatron are also briefly discussed.

43 PARTICLE ACCELERATORS↗
DOE OSTI2010

Searches for high-mass standard model Higgs boson at the Tevatron

Searches for the Standard Model Higgs boson at a center-of-mass energy of {radical}s = 1.96 TeV, using up to 5.4 fb{sup -1} of data collected with the CDF and D0 detectors at the Fermilab Tevatron collider in the mass range around 160 GeV/c{sup 2} are presented. As no significant excess is observed, limits on standard-model Higgs boson production are set.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Top quark mass and property measurements at Tevatron

The top quark, discovered in 1995 at the Fermilab Tevatron collider from CDF and D0 experiments, remains by far the most interesting particle to test standard model because of its large mass and unique properties. Having data collected about 10 fb{sup -1} of integrated luminosity of p{bar p} collision, both experiments have been studied the top quark in all the possible directions. In this article, we present the recent measurements of the top quark properties from Tevatron including the mass, width, spin correlation, and W boson helicity using t{bar t} signature.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Top differential cross section measurements (Tevatron)

Differential cross sections in the top quark sector measured at the Fermilab Tevatron collider are presented. CDF used 2.7 fb{sup -1} of data and measured the differential cross section as a function of the invariant mass of the t{bar t} system. The measurement shows good agreement with the standard model and furthermore is used to derive limits on the ratio {kappa}/M{sub Pl} for gravitons which decay to top quarks in the Randall-Sundrum model. D0 used 1.0 fb{sup -1} of data to measure the differential cross section as a function of the transverse momentum of the top-quark. The measurement shows a good agreement to the next-to-leading order perturbative QCD prediction and various other standard model predictions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Particle Physics in a Season of Change

A digest of the authors opening remarks at the 2011 Hadron Collider Physics Symposium. I have chosen my title to reflect the transitions we are living through, in particle physics overall and in hadron collider physics in particular. Data-taking has ended at the Tevatron, with {approx} 12 fb{sup -1} of {bar p}p interactions delivered to CDF and D0 at {radical}s = 1.96 TeV. The Large Hadron Collider has registered a spectacular first full-year run, with ATLAS and CMS seeing > 5 fb{sup -1}, LHCb recording {approx} 1 fb{sup -1}, and ALICE logging nearly 5 pb{sup -1} of pp data at {radical}s = 7 TeV, plus a healthy dose of Pb-Pb collisions. The transition to a new energy regime and new realms of instantaneous luminosity exceeding 3.5 x 10{sup 33} cm{sup -2} s{sup -1} has brought the advantage of enhanced physics reach and the challenge of pile-up reaching {approx} 15 interactions per beam crossing. I am happy to record that what the experiments have (not) found so far has roused some of my theoretical colleagues from years of complacency and stimulated them to think anew about what the TeV scale might hold. We theorists have had plenty of time to explore many proposals for electroweak symmetry breaking and for new physics that might lie beyond established knowledge. With so many different theoretical inventions in circulation, it is in the nature of things that most will be wrong. Keep in mind that we learn from what experiment tells us is not there, even if it is uncommon to throw a party for ruling something out. Some non-observations may be especially telling: the persistent absence of flavor-changing neutral currents, for example, seems to me more and more an important clue that we have not yet deciphered. It is natural that the search for the avatar of electroweak symmetry breaking preoccupies participants and spectators alike. But it is essential to conceive the physics opportunities before us in their full richness. I would advocate a three-fold approach: Explore, Search, Measure! The first phase of running at the LHC has brought us to two new lands - in proton-proton and lead-lead collisions - and we may well enter other new lands with each change of energy or increase of sensitivity. I believe that it will prove very rewarding to spend some time simply exploring each new landscape, without strong preconceptions, to learn what is there and, perhaps, to encounter interesting surprises. Directed searches, for which we have made extensive preparations, are of self-evident interest. Here the challenge will be to broaden the searches over time, so the searches are not too narrowly directed. Our very successful conception of particles and forces is highly idealized. We have a great opportunity to learn just how comprehensive is our network of understanding by making precise measurements and probing for weak spots, or finding more sweeping accord between theory and experiment.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Top Mass Measurements at the Tevatron

First observed in 1995, the top quark is the third-generation up-type quark of the standard model of particle physics (SM). The CDF and D0 collaborations have analyzed many t{bar t} events produced by the Tevatron collider, studying many properties of the top quark. Among these, the mass of the top quark is a fundamental parameter of the SM, since its value constrains the mass of the yet to be observed Higgs boson. The analyzed events were used to measure the mass of the top quark m{sub t} {approx_equal} 173.2 GeV/c{sup 2} with an uncertainty of less than 1 GeV/c{sup 2}. We report on the latest top mass measurements at the Tevatron, using up to 6 fb{sup -1} of data for each experiment.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Measurement of the $WZ$ Cross Section and Triple Gauge Couplings in $p \bar p$ Collisions at $\sqrt{s} = 1.96$ TeV

This Letter describes the current most precise measurement of the WZ production cross section as well as limits on anomalous WWZ couplings at a center-of-mass energy of 1.96 TeV in proton-antiproton collisions. The WZ candidates are reconstructed from decays containing three charged leptons and missing energy from a neutrino, where the charged leptons are either electrons or muons. Using data collected by the CDF II detector (7.1 fb{sup -1} of integrated luminosity), 64 candidate events are observed with the expected background contributing 8 {+-} 1 events. The measured total cross section {sigma}(p{bar p} {yields} WZ) = 3.93{sub -0.53}{sup +0.60}(stat){sub -0.46}{sup +0.59}(syst) pb is in good agreement with the standard model prediction of 3.50 {+-} 0.21. The same sample is used to set limits on anomalous WWZ couplings.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Performance study of GPUs in real-time trigger applications for HEP experiments

Graphical Processing Units (GPUs) have evolved into highly parallel, multi-threaded, multicore powerful processors with high memory bandwidth. GPUs are used in a variety of intensive computing applications. The combination of highly parallel architecture and high memory bandwidth makes GPUs a potentially promising technology for effective real-time processing for High Energy Physics (HEP) experiments. However, not much is known of their performance in real-time applications that require low latency, such as the trigger for HEP experiments. We describe an R and D project with the goal to study the performance of GPU technology for possible low latency applications, performing basic operations as well as some more advanced HEP lower-level trigger algorithms (such as fast tracking or jet finding). We present some preliminary results on timing measurements, comparing the performance of a CPU versus a GPU with NVIDIA's CUDA general-purpose parallel computing architecture, carried out at CDF's Level-2 trigger test stand. These studies will provide performance benchmarks for future studies to investigate the potential and limitations of GPUs for real-time applications in HEP experiments.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Measurements of the top quark mass at the Tevatron

The mass of the top quark (m{sub top}) is a fundamental parameter of the standard model (SM). Currently, its most precise measurements are performed by the CDF and D0 collaborations at the Fermilab Tevatron p{bar p} collider at a centre-of-mass energy of {radical}s = 1.96 TeV. We review the most recent of those measurements, performed on data samples of up to 8.7 fb{sup -1} of integrated luminosity. The Tevatron combination using up to 5.8 fb{sup -1} of data results in a preliminary world average top quark mass of m{sub top} = 173.2 {+-} 0.9 GeV. This corresponds to a relative precision of about 0.54%. We conclude with an outlook of anticipated precision the final measurement of m{sub top} at the Tevatron.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Light Gluinos in Hiding: Reconstructing R-Parity Violating Decays at the Tevatron

If gluinos exist with masses less than 200 GeV, they are copiously produced at the Tevatron, but still may not have been discovered if they decay through baryon number violating operators. We show that using cuts on jet substructure can enable a discovery with existing data and even determine the gluino's mass. This contribution has demonstrated that the Tevatron can discover new light colored particles that decay into complicated hadronic final states, by using events where these particles are produced at high p{sub T} and their boosted decay products are collimated. The recently developed techniques using jet substructure can effectively separate signal from background, allowing the new particle to appear as a jet-mass resonance. This work is a proof-of-principle, but there is significantly more work to be done. Neither of the Tevatron's two detectors have calorimetry that is as finely segmented as the LHC detectors, where most studies have been done so far, and this may reduce the jet mass resolution and restrict the Tevatron reach. Some of this resolution loss may be recovered by using tracking information, particularly at CDF [99]. On the theoretical side, the optimal cuts and jet-size for a given mass have not been determined, nor have other jet algorithms such as Cambridge/Aachen been studied. Switching to a more inclusive analysis may also improve sensitivity. The primary challenge is to keep signal efficiency high due to the low number of gluinos in the high p{sub T} tail, e.g. with m{sub {tilde g}} = 150 GeV we see 18% of gluinos with p{sub T} > 350 GeV reconstructed using R = 1.0. Therefore it may be beneficial to search for one narrow gluino candidate jet with tight constraints recoiling against another wide jet-size gluino candidate jet. The application of loose substructure cuts to the jets of the ordinary di-jet search is also interesting. If the squarks become light enough that associated squark-gluino production or squark pair production becomes sizable, then the dominant source of boosted gluinos may come from these secondary processes. This is qualitatively similar to the models studied in [65] where the hadronically decaying LSP was being produced in cascade decays of squarks and gluinos.

43 PARTICLE ACCELERATORS↗
DOE OSTI2011

Search of anomalous $Wtb$ couplins in single top quark prodution at D0

The large mass of the top quark, close to the electroweak symmetry-breaking scale, makes it a good candidate for probing physics beyond the Standard Model, including possible anomalous couplings. D0 has made measurements of single top quark production using 5.4 fb{sup -1} of integrated luminosity. We examine the data to study the Lorentz structure of the Wtb coupling. We find that the data prefer the left-handed vector coupling and set upper limits on the anomalous couplings. In 2009, the electroweak single top quark production was observed by the D0 and CDF collaborations. Electroweak production of top quarks at the Tevatron proceeds mainly via the decay of a time-like virtual W boson accompanied by a bottom quark in the s-channel (tb = t{bar b} + {bar t}b), or via the exchange of a space-like virtual W boson between a light quark and a bottom quark in the t-channel (tqb = tq{bar b} + {bar t}qb, where q refers to the light quark). For a top quark mass of 172.5 GeV, The Standard Model (SM) prediction of single top production rate at next-to-leading order with soft-gluon contributions at next-to-next-to-leading order are 1.04 {+-} 0.04 pb (s-channel) and 2.26 {+-} 0.12 pb (t-channel). The large mass of the top quark implies that it has large couplings to the electroweak symmetry breaking sector of the SM and may have non-standard interactions with the weak gauge bosons. Single top quark production provides a unique probe to study the interactions of the top quark with the W boson.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Search for the Standard Model Higgs Boson Produced in Association with a $Z$ Boson in $p\bar{p}$ Collisions at $\sqrt{s} = 1.96$ TeV

We present a search for the standard model Higgs boson produced in association with a Z boson, using up to 7.9 fb{sup -1} of integrated luminosity from p{bar p} collisions collected with the CDF II detector. We utilize several novel techniques, including multivariate lepton selection, multivariate trigger parametrization, and a multi-stage signal discriminant consisting of specialized functions trained to distinguish individual backgrounds. By increasing acceptance and enhancing signal discrimination, these techniques have significantly improved the sensitivity of the analysis above what was expected from a larger dataset alone. We observe no significant evidence for a signal, and we set limits on the ZH production cross section. For a Higgs boson with mass 115 GeV/c{sup 2}, we expect (observe) a limit of 3.9 (4.8) times the standard model predicted value, at the 95% credibility level.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Search for Scalar Top Quark Production in $p\bar{p}$ Collisions at $\sqrt{s}=1.96$ TeV

We report on a search for the supersymmetric partner of the top quark (scalar top) decaying into a charm quark and a neutralino in p{bar p} collisions at {radical}s = 1.96 TeV. The data sample, collected by the CDF II detector at the Fermilab Tevatron, corresponds to an integrated luminosity of 2.6 fb{sup -1}. Candidate events are selected by requiring two or more jets and a large imbalance in the transverse momentum. To enhance the analysis sensitivity, at least one of the jets is required to be identified as originating from a charm quark using an algorithm specifically designed for this analysis. The selected events are in good agreement with standard model predictions. In the case of large mass splitting between the scalar top quark and the neutralino we exclude a scalar top quark mass below 180 GeV/c{sup 2} at 95% confidence level.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

A Search for dark matter in events with one jet and missing transverse energy in $p\bar{p}$ collisions at $\sqrt{s} = 1.96$ TeV

We present the results of a search for dark matter production in the monojet signature. We analyze a sample of Tevatron pp collisions at {radical}s = 1.96 TeV corresponding to an integrated luminosity of 6.7 fb{sup -1} recorded by the CDF II detector. In events with large missing transverse energy and one energetic jet, we find good agreement between the standard model prediction and the observed data. We set 90% confidence level upper limits on the dark matter production rate. The limits are translated into bounds on nucleon-dark matter scattering rates which are competitive with current direct detection bounds on spin-independent interaction below a dark matter candidate mass of 5 GeV/c{sup 2}, and on spin-dependent interactions up to masses of 200 GeV/c{sup 2}.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Measurements of Top Quark Properties at the Tevatron

The top quark is the most recently discovered of the standard model quarks, and studies of its properties are important tests of the standard model. Many measurements of top properties have been produced by the CDF and D0 collaborations, which study top quarks produced in p{bar p} collisions at the Fermilab Tevatron with a center-of-mass energy {radical}s = 1.96 TeV. We describe recent results from top properties measurements at the Tevatron using datasets corresponding to integrated luminosities up to 8.7 fb{sup -1}.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Standard Model Higgs Searches at the Tevatron

We present results from the search for a standard model Higgs boson using data corresponding up to 10 fb{sup -1} of proton-antiproton collision data produced by the Fermilab Tevatron at a center-of-mass energy of 1.96 TeV. The data were recorded by the CDF and D0 detectors between March 2001 and September of 2011. A broad excess is observed between 105 < m{sub H} < 145 GeV/c{sup 2} with a global significance of 2.2 standard deviations relative to the background-only hypothesis.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Search for New Bottomlike Quark Pair Decays Q Q-Bar to (T W- ) (T-Bar W -) in Same-Charge Dilepton Events

We report the most restrictive direct limits on masses of fourth-generation down-type quarks b{prime}, and quark-like composite fermions (B or T{sub 5/3}), decaying promptly to tW{sup {-+}}. We search for a significant excess of events with two same-charge leptons (e, {mu}), several hadronic jets, and missing transverse energy. An analysis of data from p{bar p} collisions with an integrated luminosity of 2.7 fb{sup -1} collected with the CDF II detector at Fermilab yields no evidence for such a signal, setting mass limits m{sub b{prime}}, m{sub B} > 338 GeV/c{sup 2} and m{sub T{sub 5/3}} > 365 GeV/c{sup 2} at 95% confidence level.

43 PARTICLE ACCELERATORS↗