Fermilab operates the world's most intense antiproton source. Newly proposed experiments can use those antiprotons either parasitically during Tevatron Collider running or after the Tevatron Collider finishes in about 2010. In particular, the annihilation of 8 GeV antiprotons might make the world's most intense source of tagged $D^0$ mesons, and thus the best near-term opportunity to study charm mixing and, via CP violation, to search for new physics; a Penning trap and atom interferometer could be used to measure for the first time the gravitational force on antimatter.
This paper describes an experimental search for antiproton decay at the Fermilab Antiproton Accumulator. The E868 (APEX) experimental setup is described. The APEX data is expected to be sensitive to antiproton decay if the antiproton lifetimes is less than a few times 100 000 years.
Fermilab operates the world's most intense source of antiprotons. Recently various experiments have been proposed that can use those antiprotons either parasitically during Tevatron Collider running or after the Tevatron Collider finishes in about 2010. We discuss the physics goals and prospects of the proposed experiments.
A search for antiproton decay has been made at the Fermilab Antiproton Accumulator. Limits are placed on six antiproton decay modes which contain a final-state muon. At the 90% C.L. we find that tau/B(mu gamma) > 5.0 x 10^4 yr, tau/B(mu pi0) > 4.8 x 10^4 yr, tau/B(mu eta) > 7.9 x 10^3 yr, tau/B(mu gamma gamma) > 2.3 x 10^4 yr, tau/B(mu K0S > 4.3 x 10^3 yr, and tau/B(mu K0L) > 6.5 x 10^3 yr.
A search for antiproton decay has been made at the Fermilab Antiproton Accumulator. Limits are placed on thirteen antiproton decay modes. The results include the first explicit experimental limits on the muonic decay modes of the antiproton, and the first limits on the decay modes e- gamma gamma, and e- omega. The most stringent limit is for the decay mode pbar-> e- gamma. At 90% C.L. we find that tau/B(pbar-> e- gamma) > 7 x 10^5 yr. The most stringent limit for decay modes with a muon in the final state is for the decay pbar-> mu- gamma. At 90% C.L. we find that tau/B(pbar-> mu- gamma) > 5 x…
Fermilab has long had the world's most intense antiproton source. Despite this, opportunities for low-energy antiproton physics at Fermilab have in the past been limited and--with the antiproton source now exclusively dedicated to serving the needs of the Tevatron Collider--are currently nonexistent. While the future of antiproton physics at Fermilab is uncertain, the anticipated shutdown of the Tevatron in about 2009 presents the opportunity for a world-leading low-energy antiproton program. We summarize the current status of the Fermilab antiproton facility and review some current topics in …
The properties of high-mass multijet events produced at the Fermilab proton-antiproton collider are compared with leading order QCD matrix element predictions, QCD parton shower Monte Carlo predictions, and the predictions from a model in which events are distributed uniformly over the available multibody phase-space. Multijet distributions corresponding to (4N-4) variables that span the N-body parameter space are found to be well described by the QCD calculations for inclusive three-jet, four-jet, and five-jet events. The agreement between data, QCD Matrix Element calculations, and QCD parton…
We present the results of a search for the spin-singlet P-wave state hc(1 1P1) of charmonium formed through proton-antiproton annihilation at Fermilab experiment E835. The decay channels whjich were studied were ppbar -> J/psi + X -> e^+e^- + X, ppbar -> J/psi + pi0 -> e^+e^- + 2gamma, ppbar -> J/psi + pi0pi0 -> e^+e^- + 4gamma, and the neutral channel ppbar -> eta_c gamma -> (2gamma) gamma. The decay ppbar -> J/psi gamma -> e^+e^- gamma, into which 1P1 decay is forbidden by C-parity conservation, was also examined for comparison The 90% confidence upper limits for the decay channels studied i…
At the end of its operations in 2011, the Fermilab antiproton production complex consisted of a sophisticated target system, three 8-GeV storage rings (namely the Debuncher, the Accumulator and the Recycler), 25 independent multi-GHz stochastic cooling systems, the world's only relativistic electron cooling system and a team of technical experts equal to none. The accelerator complex at Fermilab supported a broad physics program including the Tevatron Collider Run II, neutrino experiments using 8-GeV and 120-GeV proton beams, as well as a test beam facility and other fixed target experiments u…
Fermilab has long had the world's most intense antiproton source, but the opportunities for medium-energy antiproton physics have been limited, and those for low-energy antiproton physics nonexistent. The conclusion of E835 brings this era to an end. While the future of antiproton physics at Fermilab remains highly uncertain, developments are occurring that may lead to a low-energy program within the next several years, with the possibility of an improved medium-energy program thereafter. These issues were considered at the recent $\bar{p}2000$ Workshop at Illinois Institute of Technology. I s…
Fermilab operates the world's most intense antiproton source. Newly proposed experiments can use those antiprotons either parasitically during Tevatron Collider running or after the end of the Tevatron Collider program. For example, the annihilation of 5 to 8 GeV antiprotons is expected to yield world-leading sensitivities to hyperon rare decays and CP violation. It could also provide the world's most intense source of tagged D^0 mesons, and thus the best near-term opportunity to study charm mixing and, via CP violation, to search for new physics. Other measurements that could be made include …
We report a measurement of the fraction of events with a large pseudorapidity gap $Δη$ within the pseudorapidity region available to the proton dissociation products $X$ in $\bar p+p\to \bar p+X$. For a final state $\bar p$ of fractional momentum loss $ξ_{\bar p}$ and 4-momentum transfer squared $t_{\bar p}$ within $0.06<ξ_{\bar p}<0.09$ and $|t_{\bar p}|<1.0$ [0.2] GeV$^2$ at $\sqrt s=1800$ [630] GeV, the fraction of events with $Δη>3$is found to be $0.246\pm 0.001 {\rm (stat)}\pm 0.042 {\rm (syst)}$ [$0.184\pm 0.001 {\rm (stat)}\pm 0.043 {\rm (syst)}$]. Our results are compared with gap frac…
Selected recent quantum chromodynamics (QCD) measurements are reviewed for Fermilab Run II Tevatron proton-antiproton collisions studied by the Collider Detector at Fermilab (CDF) and DZero Collaborations at a centre-of-mass energy of sqrt{s}=1.96 TeV. Tantamount to Rutherford scattering studies at the TeV scale, inclusive jet and dijet production cross-section measurements are used to seek and constrain new particle physics phenomena, test perturbative QCD calculations, inform parton distribution function (PDF) determinations, and extract a precise value of the strong coupling constant, alpha…
We report on a measurement of the fraction of events with a W or Z boson which are produced diffractively in antiproton-proton collisions at a center of mass energy of 1.96 TeV, using data from 0.6 inverse femtobarns of integrated luminosity collected with the CDF-II detector equipped with a Roman-pot spectrometer that detects the antiproton (pbar) from pbar+p --> pbar+[X+W/Z]. We find that (1.00+/- 0.11)% of Ws and (0.88+/-0.22)% of Zs are produced diffractively in a region of antiproton or proton fractional momentum loss (ξ) of 0.03<ξ<0.10 and 4-momentum transferred squared t of -1<t<0 (GeV/…
We present the results of a search in proton-antiproton collisions at sqrt(s) = 1.8 TeV for anomalous production of events containing a photon with large transverse energy and a lepton (e or mu) with large transverse energy, using 86 pb^{-1} of data collected with the Collider Detector at Fermilab during the 1994-95 collider run at the Fermilab Tevatron. The presence of large missing transverse energy, additional photons, or additional leptons in these events is also analyzed. The results are consistent with standard model expectations, with the possible exception of photon-lepton events with …
Fermilab operates the world's most intense antiproton source, now exclusively dedicated to serving the needs of the Tevatron Collider. The anticipated 2009 shutdown of the Tevatron presents the opportunity for a world-leading low- and medium-energy antiproton program. We summarize the status of the Fermilab antiproton facility and review physics topics for which a future experiment could make the world's best measurements.
We report a measurement of the diffractive structure function $F_{jj}^D$ of the antiproton obtained from a study of dijet events produced in association with a leading antiproton in $\bar pp$ collisions at $\sqrt s=630$ GeV at the Fermilab Tevatron. The ratio of $F_{jj}^D$ at $\sqrt s=630$ GeV to $F_{jj}^D$ obtained from a similar measurement at $\sqrt s=1800$ GeV is compared with expectations from QCD factorization and with theoretical predictions. We also report a measurement of the $ξ$ ($x$-Pomeron) and $β$ ($x$ of parton in Pomeron) dependence of $F_{jj}^D$ at $\sqrt s=1800$ GeV. In the re…
We present the strategy which has been used recently to optimize integrated luminosity at the Fermilab Tevatron proton-antiproton collider. We use a relatively simple model where we keep the proton intensity fixed, use parameters from fits to the luminosity decay of recent stores as a function of initial antiproton intensity (stash size), and vary the stash size to optimize the integrated luminosity per week. The model assumes a fixed rate of antiproton production, that a store is terminated as soon as the target stash size for the next store is reached, and that the only downtime is due to st…
A search for antiproton decay has been made at the Fermilab Antiproton Accumulator. Limits are placed on fifteen antiproton decay modes. The results are used to place limits on the characteristic mass scale Mx that could be associated with CPT-violation accompanied by baryon number violation.
A long time ago, at a laboratory far, far away, the Fermilab Tevatron collided protons and antiprotons at $\sqrt{s} = 1.96$ TeV. The CDF and D0 experiments each recorded datasets of about 10 fb$^{-1}$. As such experiments may never be repeated, these are unique datasets that allow for unique measurements. This presentation describes recent results from the two experiments on top-quark production rates, spin orientations, and production asymmetries, which are all probes of the $p\bar{p}$ initial state.
Fermilab operates the world's most intense antiproton source, now exclusively dedicated to serving the needs of the Tevatron Collider. The anticipated 2009 shutdown of the Tevatron presents the opportunity for world-leading low- and medium-energy antiproton programs. We summarize the status of the Fermilab antiproton facility and review physics topics for which a future experiment could make the world's best measurements.
Fermilab operates the world's most intense antiproton source. Recently proposed experiments can use those antiprotons either parasitically during Tevatron Collider running or after the Tevatron Collider finishes in about 2011. For example, the annihilation of 8 GeV antiprotons might make the world's most intense source of tagged D^0 mesons, and thus the best near-term opportunity to study charm mixing and search for new physics via its CP-violation signature. Other possible precision measurements include properties of the X(3872) and the charmonium system. An experiment using a Penning trap an…
Fermilab operates the world's most intense antiproton source. Newly proposed experiments can use those antiprotons either parasitically during Tevatron Collider running or after the Tevatron Collider finishes. For example, the annihilation of 8 GeV antiprotons is expected to yield world-leading sensitivities to hyperon rare decays and CP violation. It could also provide the world's most intense source of tagged D^0 mesons, and thus the best near-term opportunity to study charm mixing and, via CP violation, to search for new physics. Other precision measurements that could be made include prope…
Fermilab experiment E835 has observed proton-antiproton annihilation production of the charmonium state chi_c0 and its subsequent decay into pi^0 pi^0. Although the resonant amplitude is an order of magnitude smaller than that of the non-resonant continuum production of pi^0 pi^0, an enhanced interference signal is evident. A partial wave expansion is used to extract physics parameters. The amplitudes J=0 and 2, of comparable strength, dominate the expansion. Both are accessed by L=1 in the entrance proton-antiproton channel. The product of the input and output branching fractions is determine…
We present the first evidence of WW+WZ production with lepton+jets final states at a hadron collider. The data correspond to 1.07 inverse femtobarns of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider in proton-antiproton collisions at sqrt(s)=1.96 TeV. The observed cross section for WW+WZ production is 20.2 +/- 4.5 pb, consistent with the SM prediction of 16.1 +/- 0.9 pb. The probability for background fluctuations to produce an excess equal to or larger than that observed is estimated to be 5.4e-6, corresponding to a significance of 4.4 standard deviatio…
We present an analysis of dilepton events originating from top-antitop production in proton-antiproton collisions at sqrt{s}=1.8 TeV at the Fermilab Tevatron Collider. The sample corresponds to an integrated luminosity of 109+-7 pb^{-1}. We observe 9 candidate events, with an estimated background of 2.4+-0.5 events. We determine the mass of the top quark to be M_top = 161+-17(stat.)+-10(syst.) GeV/c^2. In addition we measure a top-antitop production cross section of 8.2+4.4-3.4 pb (where M_top = 175 GeV/c^2 has been assumed for the acceptance estimate).
We present recent results from the Collider Detector at Fermilab (CDF) and D0 experiments using data from proton-antiproton collisions with sqrt(s) = 1.96 TeV at Run II of the Fermilab Tevatron. New physics may appear in events with high transverse momentum objects, including photons and quark or gluon jets. The results described here are of signature-based searches and model-based searches probing supersymmetry, leptoquarks, 4th generation quarks, and large extra dimensions.
This is a short paper summarising a presentation of the evolution of the Fermilab program for the next five to ten years. Emphasis is given to the Fermilab accelerator complex, but external collaboration is emphasised.
Fermilab operates the world's most intense antiproton source. Newly proposed experiments can use those antiprotons either parasitically during Tevatron Collider running or after the Tevatron Collider finishes in about 2011. For example, the annihilation of 8 GeV antiprotons might make the world's most intense source of tagged D^0 mesons, and thus the best near-term opportunity to study charm mixing and, via CP violation, to search for new physics. Other potential measurements include sensitive studies of hyperons and of the mysterious X, Y, and Z states. Production of antihydrogen in flight ca…
This dissertation presents an experimental search for the Standard Model Higgs boson produced in association to the W boson in proton antiproton collisions at a center of mass energy of 1.96 TeV and recorded with the Collider Detector at Fermilab. We improve the sensitivity of the WH search by 17% through increased signal yield by 33% by introducing a novel method to reconstruct charged lepton candidates based on an isolated track, as well as a novel method to combine triggers in order to maximize the signal yield and yet not use an OR between triggers. The observed (median expected) 95% confi…
Fermilab's hadron physics research continues in all its accelerator-based programs. These efforts will be identified, and the optimization of the Fermilab schedules for physics will be described. In addition to the immediate plans, the Fermilab Long Range Plan will be cited, and the status and potential role of a new proton source, the Proton Driver, will be described.
Today, hadron physics research occurs at Fermilab as parts of broader experimental programs. This is very likely to be the case in the future. Thus, much of this presentation focuses on our vision of that future - a future aimed at making Fermilab the host laboratory for the International Linear Collider (ILC). Given the uncertainties associated with the ILC - the level of needed R&D, the ILC costs, and the timing - Fermilab is also preparing for other program choices. I will describe these latter efforts, efforts focused on a Proton Driver to increase the numbers of protons available for expe…
Recent results from CERN experiment WA89 have shown that charmed baryons and particularly charmed-strange baryons have a significant cross section in $Σ^-$ beams. Fermilab experiment 781, which is currently under construction, will utilize this fact to pursue a broad program of high statistics studies of charmed baryons in the next Fermilab fixed target run.
Top quark pair production at proton-antiproton colliders is known to exhibit a forward-backward asymmetry due to higher-order QCD effects. We explore how this asymmetry might be studied at the Fermilab Tevatron, including how the asymmetry depends on the kinematics of extra hard partons. We consider results for top quark pair events with one and two additional hard jets. We further note that a similar asymmetry, correlated with the presence of jets, arises in specific models for parton showers in Monte Carlo simulations. We conclude that the measurement of this asymmetry at the Tevatron will b…
The most recent results of the top-quark mass measurements at the Tevatron at Fermilab are presented. Data were collected in proton-antiproton collisions at sqrt{s}=1.96 TeV by the CDF and D0 experiments. Top quark mass measurements in the lepton+jets, dilepton and alljet final states as well as their combination and the extraction of the mass from the cross-section measurement are presented.
This review gives an overview of most recent measurements of top quark production cross sections including differential cross sections and searches for new physics in the top quark sector. Datasets corresponding to an integrated luminosity of up to 5.7 fb-1 are presented which were taken at the Tevatron proton-antiproton collider at a center-of-mass energy of sqrt(s)=1.96 TeV at Fermilab.
We present an idea for a future D0-D0bar mixing and CP violation experiment to run at the Fermilab Tevatron. We estimate that in three years of running, such an experiment could reconstruct an order of magnitude more flavor-tagged D0->K+pi- decays than will be reconstructed by the B-factory experiments with their full data sets. The resulting sensitivity to CP-violating parameters |q/p| and Arg(q/p) is calculated from a global fit to CP-violating observables, and it is found to be much greater than current world sensitivity.
A summary of the most recent results on top quark physics obtained at Fermilab's Tevatron proton-antiproton collider, operating at a centre of mass energy of 1.96 TeV, is presented. Measurements of the top pair and single top quark production cross sections, the investigation of top quark decay properties, the precision measurement of the top quark mass as well as searches for physics beyond the standard model are discussed.
Results on diffraction from the Fermilab Tevatron collider obtained by the CDF II Collaboration using data from proton-antiproton collisions at a c.m.s. energy of 1.96 TeV are reviewed and compared with theoretical expectations. Implications for predictions of exclusive Higgs boson production rates at the Large Hadron Collider are discussed.
Preliminary results on diffractive W and Z production in proton-antiproton collisions at a c.m.s. energy of 1.96 TeV are presented and discussed. Differential cross sections are measured from data collected with the CDF-II detector at the Fermilab Tevatron collider using a Roman pot spectrometer that detects leading antiprotons. The ratio of diffractive to total W production rates (diffractive fraction) agrees with that measured by CDF in Run-I using a rapidity gap diffractive signature. The W and Z diffractive fractions are equal within the measurement uncertainties, which are dominated by a …
The Tevatron proton-antiproton collider at Fermilab operates at a centre of mass energy of 1.96 TeV and is currently the only source for the production of top quarks. Recent D0 results on the top quark's production cross section and its properties such as mass, helicity of the W boson in its decay and branching fraction B(t -> Wb) are presented, and probe the validity of the Standard Model.
We present the first evidence from a hadron collider of WW+WZ production with semi-leptonic decays. The data were recorded by the D0 detector at the Fermilab Tevatron and correspond to 1.07 inverse femtobarn of integrated luminosity obtained in proton-antiproton collisions at sqrt(s) = 1.96 TeV. The cross section observed for WW+WZ production is 20.2 +- 4.5 pb with a significance of 4.4 standard deviations.
The Tevatron proton-antiproton collider at Fermilab continues operation as the world's highest energy particle accelerator by delivering luminosity at a center-of-mass energy of 1.96 TeV. We review recent performance and plans for the remainder of Run 2.
An overview of the recent measurements of the top quark properties in proton antiproton collisions at \sqrt{s}=1.96 TeV is presented.These measurements are based on 5.4 -- 8.7 fb^-1 of data collected with the D0 and CDF experiments at the Fermilab Tevatron collider. The top quark mass and width measurements, studies of the spin correlation in top quark pair production, W boson helicity measurement, searches for anomalous top quark couplings and Lorentz invariance violation are discussed.
The Tevatron proton-antiproton collider at Fermilab with its centre of mass energy of 1.96 TeV is currently the only source for the production of top quarks. This report reflects the current status of measurements of the top quark pair production cross section and properties performed by the CDF and D0 Collaborations. Utilising datasets of up to two inverse fb, these measurements allow unprecedented precision in probing the validity of the Standard Model.
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 proton-antiproton collisions at the Fermilab Tevatron with a center-of-mass energy sqrt{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.
Searches for Physics beyond the Standard Model have entered an exciting new phase: the complete HERA data samples obtained until the end of operations in the Summer of 2007 are now available for analysis. ZEUS and H1 have each collected about 0.5 fb^{-1} of lepton proton data, distributed over electron and positron running, and over different lepton beam polarisations. At the same time the Fermilab Tevatron proton-antiproton collider is accumulating data at unprecedented rates, with current analyses based on up to 3 fb^{-1}. The Tevatron experiments DZERO and CDF have each already recorded ove…
One component of the future international Facility for Antiproton and Ion Research - FAIR is directed towards studies of hadronic matter at the sub-nuclear level with beams of antiprotons. These studies focus on two key aspects: confinement of quarks and the generation of the hadron masses. These goals will be pursued by performing precision measurements of charged and neutral decay products from antiproton-proton annihilation in the charmonium mass region. In this report an overview of the charmonium issues relevant to PANDA will be presented.
This article is a short summary of the talk presented at 2014 Instrumentation Conference in Novosibirsk about Fermilab's experimental program and future plans. It includes brief description of the P5 long term planning progressing in US as well as discussion of the future accelerators considered at Fermilab.
One of the great challenges of QCD is trying to understand the origin of the nucleon spin. Several decades of experimental measurements have shown that our current understanding is incomplete if only the quark and gluon spin contribution is considered. Over the last few years it has become increasingly clear that the contribution from the orbital angular momentum of the quarks and gluons has to be included as well. For instance, the sea quark orbital contribution remains largely unexplored. Measurements accessing the sea quark Sivers distribution will provide a probe of the sea quark orbital c…
High-beta superconducting radiofrequency (SRF) elliptical cavities are being developed for several accelerator projects including Project X, the European XFEL, and the International Linear Collider (ILC). Fermilab has recently established an extensive infrastructure for SRF cavity R&D for future accelerators, including cavity surface processing and testing and cavity assembly into cryomodules. Some highlights of the global effort in SRF R&D toward improving cavity performance, and Fermilab SRF cavity R&D in the context of global projects are reviewed.
