P. C. Bhat

We report the observation of the X(3872) in the J/psipi(+)pi(-) channel, with J/psi decaying to mu(+)mu(-), in pp collisions at sqrt[s]=1.96 TeV. Using approximately 230 pb(-1) of data collected with the Run II D0 detector, we observe 522+/-100 X(3872) candidates. The mass difference between the X(3872) state and the J/psi is measured to be 774.9+/-3.1(stat)+/-3.0(syst) MeV/c(2). We have investigated the production and decay characteristics of the X(3872) and find them to be similar to those of the psi(2S) state.

We report observation of the electroweak production of single top quarks in pp[over ] collisions at sqrt[s]=1.96 TeV based on 2.3 fb(-1) of data collected by the D0 detector at the Fermilab Tevatron Collider. Using events containing an isolated electron or muon and missing transverse energy, together with jets originating from the fragmentation of b quarks, we measure a cross section of sigma(pp[over ]--> tb + X, tqb + X) = 3.94 + or - 0.88 pb. The probability to measure a cross section at this value or higher in the absence of signal is 2.5 x 10(-7), corresponding to a 5.0 standard deviation significance for the observation.

We combine searches by the CDF and D0 Collaborations for the associated production of a Higgs boson with a W or Z boson and subsequent decay of the Higgs boson to a bottom-antibottom quark pair. The data, originating from Fermilab Tevatron pp collisions at √s = 1.96 TeV, correspond to integrated luminosities of up to 9.7 fb(-1). The searches are conducted for a Higgs boson with mass in the range 100-150 GeV/c(2). We observe an excess of events in the data compared with the background predictions, which is most significant in the mass range between 120 and 135 GeV/c(2). The largest local significance is 3.3 standard deviations, corresponding to a global significance of 3.1 standard deviations. We interpret this as evidence for the presence of a new particle consistent with the standard model Higgs boson, which is produced in association with a weak vector boson and decays to a bottom-antibottom quark pair.

We present a measurement of forward-backward asymmetry in top quark-antiquark production in proton-antiproton collisions in the final state containing a lepton and at least four jets. Using a dataset corresponding to an integrated luminosity of $5.4\,\mathrm {fb}^{-1}$, collected by the \DZ\ experiment at the Fermilab Tevatron Collider, we measure the \ttbar\ forward-backward asymmetry to be $(9.2 \pm 3.7)$% at the reconstruction level. When corrected for detector acceptance and resolution, the asymmetry is found to be $(19.6 \pm 6.5)$%. We also measure a corrected asymmetry based on the lepton from a top quark decay, found to be $(15.2 \pm 4.0)$%. The results are compared to predictions based on the next-to-leading-order QCD generator {\sc mc@nlo}. The sensitivity of the measured and predicted asymmetries to the modeling of gluon radiation is discussed.

We report on a measurement of the inclusive jet cross section in pp[over ] collisions at a center-of-mass energy sqrt[s]=1.96 TeV using data collected by the D0 experiment at the Fermilab Tevatron Collider corresponding to an integrated luminosity of 0.70 fb;{-1}. The data cover jet transverse momenta from 50 to 600 GeV and jet rapidities in the range -2.4 to 2.4. Detailed studies of correlations between systematic uncertainties in transverse momentum and rapidity are presented, and the cross section measurements are found to be in good agreement with next-to-leading order QCD calculations.

We present the first measurement of the integrated forward-backward charge asymmetry in top-quark–top-antiquark pair (t¯t) production in proton-antiproton (p¯p) collisions in the lepton+jets final state. Using a b-jet tagging algorithm and kinematic reconstruction assuming t¯t+X production and decay, a sample of 0.9 fb−1 of data, collected by the D0 experiment at the Fermilab Tevatron Collider, is used to measure the asymmetry for different jet multiplicities. The result is also used to set upper limits on t¯t+X production via a Z′ resonance.Received 7 December 2007DOI:https://doi.org/10.1103/PhysRevLett.100.142002©2008 American Physical Society

From an analysis of the flavor-tagged decay Bs0-->J/psiphi we obtain the width difference between the Bs0 light and heavy mass eigenstates, DeltaGammas = 0.19+/-0.07(stat)(-0.01)+0.02(syst) ps(-1), and the CP-violating phase, phi s= -0.57(-0.30)+0.24(stat)(-0.02)+0.08(syst). The allowed 90% CL intervals of DeltaGammas and phi s are 0.06 < DeltaGammas < 0.30 ps(-1) and -1.20 < phi s < 0.06, respectively. The data sample corresponds to an integrated luminosity of 2.8 fb(-1) accumulated with the D0 detector at the Fermilab Tevatron collider.

We report results of a study of the B(s)(0) oscillation frequency using a large sample of B(s)(0) semileptonic decays corresponding to approximately 1 fb(-1) of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron Collider in 2002-2006. The amplitude method gives a lower limit on the B(s)(0) oscillation frequency at 14.8 ps(-1) at the 95% C.L. At delta m(s) = 19 ps(-1), the amplitude deviates from the hypothesis A= 0(1) by 2.5 (1.6) standard deviations, corresponding to a two-sided C.L. of 1% (10%). A likelihood scan over the oscillation frequency, delta m(s), gives a most probable value of 19 ps(-1) and a range of 17 < delta m(s) < 21 ps(-1)at the 90% C.L., assuming Gaussian uncertainties. This is the first direct two-sided bound measured by a single experiment. If delta m(s) lies above 22 ps(-1), then the probability that it would produce a likelihood minimum similar to the one observed in the interval 16-22 ps(-1) is (5.0 +/- 0.3)%.

We have used a sample of photon+3 jets events collected by the D0 experiment with an integrated luminosity of about 1 fb^-1 to determine the fraction of events with double parton scattering (f_DP) in a single ppbar collision at sqrt{s}=1.96 TeV. The DP fraction and effective cross section (sigma_eff), a process-independent scale parameter related to the parton density inside the nucleon, are measured in three intervals of the second (ordered in pT) jet transverse momentum pT_jet2 within the range 15 < pT_jet2 < 30 GeV. In this range, f_DP varies between 0.23 < f_DP < 0.47, while sigma_eff has the average value sigma_eff_ave = 16.4 +- 0.3(stat) +- 2.3(syst) mb.

We measure the charge asymmetry A ≡ (N++ - N--)/(N++ + N--) of like-sign dimuon events in 6.1 fb-1 of pp collisions recorded with the D0 detector at a center-of-mass energy square root(s) = 1.96 TeV at the Fermilab Tevatron collider. From A we extract the like-sign dimuon charge asymmetry in semileptonic b-hadron decays: A(sl)(b) = -0.009 57 ± 0.002 51(stat) ± 0.001 46(sys). It differs by 3.2 standard deviations from the standard model prediction A(sl)(b)(SM) = (-2.3(-0.6)(+0.5)) × 10(-4), and provides first evidence of anomalous CP violation in the mixing of neutral B mesons.

We combine searches by the CDF and D0 collaborations for a Higgs boson decaying to W+W-. The data correspond to an integrated total luminosity of 4.8 (CDF) and 5.4 (D0) fb-1 of p-pbar collisions at sqrt{s}=1.96 TeV at the Fermilab Tevatron collider. No excess is observed above background expectation, and resulting limits on Higgs boson production exclude a standard-model Higgs boson in the mass range 162-166 GeV at the 95% C.L.

We report evidence for a narrow structure, X(5568), in the decay sequence X(5568)→B_{s}^{0}π^{±}, B_{s}^{0}→J/ψϕ, J/ψ→μ^{+}μ^{-}, ϕ→K^{+}K^{-}. This is evidence for the first instance of a hadronic state with valence quarks of four different flavors. The mass and natural width of this state are measured to be m=5567.8±2.9(stat)_{-1.9}^{+0.9}(syst) MeV/c^{2} and Γ=21.9±6.4(stat)_{-2.5}^{+5.0}(syst) MeV/c^{2}. If the decay is X(5568)→B_{s}^{*}π^{±}→B_{s}^{0}γπ^{±} with an unseen γ, m(X(5568)) will be shifted up by m(B_{s}^{*})-m(B_{s}^{0})∼49 MeV/c^{2}. This measurement is based on 10.4 fb^{-1} of pp[over ¯] collision data at sqrt[s]=1.96 TeV collected by the D0 experiment at the Fermilab Tevatron collider.

We measure the charge asymmetry $A$ of like-sign dimuon events in 6.1 fb$^{-1}$ of $p\bar{p}$ collisions recorded with the D0 detector at a center-of-mass energy $\sqrt{s} = 1.96$ TeV at the Fermilab Tevatron collider. From $A$, we extract the like-sign dimuon charge asymmetry in semileptonic $b$-hadron decays: $\aslb = -0.00957 \pm 0.00251 ({\rm stat}) \pm 0.00146 ({\rm syst})$. This result differs by 3.2 standard deviations from the standard model prediction $\aslb(SM) = (-2.3^{+0.5}_{-0.6}) \times 10^{-4}$ and provides first evidence of anomalous CP-violation in the mixing of neutral $B$ mesons.

The top quark is the heaviest known elementary particle, with a mass about 40 times larger than the mass of its isospin partner, the bottom quark. It decays almost 100% of the time to a $W$ boson and a bottom quark. Using top-antitop pairs at the Tevatron proton-antiproton collider, the CDF and D0 Collaborations have measured the top quark's mass in different final states for integrated luminosities of up to $5.8\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$. This paper reports on a combination of these measurements that results in a more precise value of the mass than any individual decay channel can provide. It describes the treatment of the systematic uncertainties and their correlations. The mass value determined is $173.18\ifmmode\pm\else\textpm\fi{}0.56\text{ }(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.75\text{ }(\mathrm{syst})\text{ }\text{ }\mathrm{GeV}$ or $173.18\ifmmode\pm\else\textpm\fi{}0.94\text{ }\text{ }\mathrm{GeV}$, which has a precision of $\ifmmode\pm\else\textpm\fi{}0.54%$, making this the most precise determination of the top-quark mass.

We present a search for charged Higgs bosons in top quark decays. We analyze the \eplus, \muplus, $ee$, $e\mu$, $\mu\mu$, \etau and \mutau final states from top quark pair production events, using data from about 1${\text{fb}}^{-1}$ of integrated luminosity recorded by the \dzero experiment at the Fermilab Tevatron Collider. We consider different scenarios of possible charged Higgs boson decays, one where the charged Higgs boson decays purely hadronically into a charm and a strange quark, another where it decays into a $\tau$ lepton and a $\tau$ neutrino and a third one where both decays appear. We extract limits on the branching ratio $B(t\to H^+ b)$ for all these models. We use two methods, one where the $t\bar{t}$ production cross section is fixed, and one where the cross section is fitted simultaneously with $B(t\to H^+b)$. Based on the extracted limits, we exclude regions in the charged Higgs boson mass and $\tan \beta$ parameter space for different scenarios of the minimal supersymmetric standard model.

We present an updated measurement of the anomalous like-sign dimuon charge asymmetry Aslb for semi-leptonic $b$-hadron decays in 9.0 fb^-1 of p pbar collisions recorded with the D0 detector at a center-of-mass energy of sqrt{s} = 1.96 TeV at the Fermilab Tevatron collider. We obtain Aslb = (-0.787 +- 0.172(stat) +- 0.093 (syst))%. This result differs by 3.9 standard deviations from the prediction of the standard model and provides evidence for anomalously large CP violation in semi-leptonic neutral B decay. The dependence of the asymmetry on the muon impact parameter is consistent with the hypothesis that it originates from semi-leptonic b-hadron decays.

We combine searches by the CDF and D0 Collaborations for the standard model Higgs boson with mass in the range 90–200 GeV/c2 produced in the gluon-gluon fusion, WH, ZH, t¯tH, and vector boson fusion processes, and decaying in the H→b¯b, H→W+W−, H→ZZ, H→τ+τ−, and H→γγ modes. The data correspond to integrated luminosities of up to 10 fb−1 and were collected at the Fermilab Tevatron in p¯p collisions at √s=1.96 TeV. The searches are also interpreted in the context of fermiophobic and fourth generation models. We observe a significant excess of events in the mass range between 115 and 140 GeV/c2. The local significance corresponds to 3.0 standard deviations at mH=125 GeV/c2, consistent with the mass of the Higgs boson observed at the LHC, and we expect a local significance of 1.9 standard deviations. We separately combine searches for H→b¯b, H→W+W−, H→τ+τ−, and H→γγ. The observed signal strengths in all channels are consistent with the presence of a standard model Higgs boson with a mass of 125 GeV/c2.18 MoreReceived 26 March 2013DOI:https://doi.org/10.1103/PhysRevD.88.052014© 2013 American Physical Society

We report an updated measurement of the CP-violating phase, $\phi_s^{J/\psi \phi}$, and the decay-width difference for the two mass eigenstates, $\Delta \Gamma_s$, from the flavor-tagged decay $B_s^0 \rightarrow J/\psi \phi$. The data sample corresponds to an integrated luminosity of 8.0 fb$^{-1}$ accumulated with the D0 detector using $p \barp$ collisions at $\sqrt{s} = 1.96$ TeV produced at the Fermilab Tevatron collider. The 68% confidence level intervals, including systematic uncertainties, are $\Delta \Gamma_s = 0.163 +0.065 -0.064 ps^{-1}$ and $\phi_s^{J/\psi \phi} = -0.55 +0.38 -0.36$. The $p$-value for the Standard Model point is 29.8%.

We present a measurement of the W boson mass using data corresponding to 4.3fb^-1 of integrated luminosity collected with the D0 detector during Run II at the Fermilab Tevatron p\bar{p} collider. With a sample of 1,677,394 W -> e\nu candidate events, we measure M_W = 80.367 +/- 0.026 GeV. This result is combined with an earlier D0 result determined using an independent Run II data sample, corresponding to 1fb^-1 of integrated luminosity, to yield M_W = 80.375 +/- 0.023 GeV.

We investigate the decay B + → J/ψφK + in a search for the X(4140) state, a narrow threshold resonance in the J/ψφ system.The data sample corresponds

A program to build a lepton-collider Higgs factory, to precisely measure the couplings of the Higgs boson to other particles, followed by a higher energy run to establish the Higgs self-coupling and expand the new physics reach, is widely recognized as a primary focus of modern particle physics. We propose a strategy that focuses on a new technology and preliminary estimates suggest that can lead to a compact, affordable machine. New technology investigations will provide much needed enthusiasm for our field, resulting in trained workforce. This cost-effective, compact design, with technologies useful for a broad range of other accelerator applications, could be realized as a project in the US. Its technology innovations, both in the accelerator and the detector, will offer unique and exciting opportunities to young scientists. Moreover, cost effective compact designs, broadly applicable to other fields of research, are more likely to obtain financial support from our funding agencies.

Abstract Construction of an e + e - Higgs factory has been identified as a major goal for particle physics. Such a collider will offer precise measurements of the Higgs bosons couplings to other particles. A Higgs factory extendable in energy can also establish the Higgs self-coupling, measure the Higgs coupling to the top quark, and expand the reach to probe new phenomena. We propose a strategy for an energy-extendable Higgs factory based on a new linear accelerator technology. This strategy offers a compact and cost-effective design that could be realized as an accelerator project in the US. The core technologies to be developed have broad applications to accelerators for medicine and for X-ray science. The challenge of realizing these technologies will offer unique and exciting opportunities to young scientists.

Abstract A multi-TeV muon collider offers a spectacular opportunity in the direct exploration of the energy frontier. Offering a combination of unprecedented energy collisions in a comparatively clean leptonic environment, a high energy muon collider has the unique potential to provide both precision measurements and the highest energy reach in one machine that cannot be paralleled by any currently available technology. The topic generated a lot of excitement in Snowmass meetings and continues to attract a large number of supporters, including many from the early career community. In light of this very strong interest within the US particle physics community, Snowmass Energy, Theory and Accelerator Frontiers created a cross-frontier Muon Collider Forum in November of 2020. The Forum has been meeting on a monthly basis and organized several topical workshops dedicated to physics, accelerator technology, and detector R&amp;D. Findings of the Forum are summarized in this report.

The D0 collaboration has performed a measurement of the top quark mass based on six candidate events for the process t tbar -&gt; b W+ bbar W-, where the W bosons decay to e nu or mu nu. This sample was collected during an exposure of the D0 detector to an integrated luminosity of 125 pb^-1 of sqrt(s)=1.8 TeV p-pbar collisions. We obtain mt = 168.4 +- 12.3 (stat) +- 3.7 (sys) GeV/c^2, consistent with the measurement obtained using single-lepton events. Combination of the single-lepton and dilepton results yields mt = 172.0 +- 7.5 GeV/c^2.

We determine the top quark mass mt using tt¯ pairs produced in the DØ detector by s=1.8TeV pp¯ collisions in a 125pb−1 exposure at the Fermilab Tevatron. We make a two constraint fit to mt in tt¯→bW+b¯W− final states with one W boson decaying to qq¯ and the other to eν or μν. Likelihood fits to the data yield mt(l+jets)=173.3±5.6(stat)±5.5(syst) GeV/c2. When this result is combined with an analysis of events in which both W bosons decay into leptons, we obtain mt=172.1±5.2(stat)±4.9(syst) GeV/c2. An alternate analysis, using three constraint fits to fixed top quark masses, gives mt(l+jets)=176.0±7.9(stat)±4.8(syst) GeV/c2, consistent with the above result. Studies of kinematic distributions of the top quark candidates are also presented. 14.65.Ha, 13.85.Ni, 13.85.QkReceived 27 January 1998DOI:https://doi.org/10.1103/PhysRevD.58.052001©1998 American Physical Society

We present a measurement of the shape of the boson rapidity distribution for p¯p→Z/γ∗→e+e−+X events at a center-of-mass energy of 1.96 TeV. The measurement is made for events with electron-positron mass 71<Mee<111 GeV and uses 0.4 fb−1 of data collected at the Fermilab Tevatron collider with the D0 detector. This measurement significantly reduces the uncertainties on the rapidity distribution in the forward region compared with previous measurements. Predictions of next-to-next-to-leading order (NNLO) QCD are found to agree well with the data over the full rapidity range.Received 16 February 2007DOI:https://doi.org/10.1103/PhysRevD.76.012003©2007 American Physical Society

A data sample corresponding to an integrated luminosity of 2.1 fb−1 collected by the DØ detector at the Fermilab Tevatron Collider was analyzed to search for squarks and gluinos produced in pp¯ collisions at a center-of-mass energy of 1.96 TeV. No evidence for the production of such particles was observed in topologies involving jets and missing transverse energy, and 95% C.L. lower limits of 379 GeV and 308 GeV were set on the squark and gluino masses, respectively, within the framework of minimal supergravity with tanβ=3, A0=0, and μ<0. The corresponding previous limits are improved by 54 GeV and 67 GeV.

The D0 Collaboration presents first evidence for the production of single top quarks at the Fermilab Tevatron pp[over ] collider. Using a 0.9 fb(-1) dataset, we apply a multivariate analysis to separate signal from background and measure sigma(pp[over ]-->tb+X,tqb+X)=4.9+/-1.4 pb. The probability to measure a cross section at this value or higher in the absence of a signal is 0.035%, corresponding to a 3.4 standard deviation significance. We use the cross section measurement to directly determine the Cabibbo-Kobayashi-Maskawa matrix element that describes the Wtb coupling and find 0.68<|V(tb)|</=1 at 95% C.L. within the standard model.

We present a measurement of the shape of the $Z/{\ensuremath{\gamma}}^{*}$ boson transverse momentum (${q}_{T}$) distribution in $p\overline{p}\ensuremath{\rightarrow}Z/{\ensuremath{\gamma}}^{*}\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}}+X$ events at a center-of-mass energy of 1.96 TeV using $0.98\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of data collected with the D0 detector at the Fermilab Tevatron collider. The data are found to be consistent with the resummation prediction at low ${q}_{T}$, but above the perturbative QCD calculation in the region of ${q}_{T}&gt;30\text{ }\text{ }\mathrm{GeV}/c$. Using events with ${q}_{T}&lt;30\text{ }\text{ }\mathrm{GeV}/c$, we extract the value of ${g}_{2}$, one of the nonperturbative parameters for the resummation calculation. Data at large boson rapidity $y$ are compared with the prediction of resummation and with alternative models that employ a resummed form factor with modifications in the small Bjorken $x$ region of the proton wave function.

We report the first direct observation of the strange b baryon Xi(b)- (Xi(b)+). We reconstruct the decay Xi(b)- -->J/psiXi-, with J/psi-->mu+mu-, and Xi--->Lambdapi--->ppi-pi- in pp collisions at square root of s =1.96 TeV. Using 1.3 fb(-1) of data collected by the D0 detector, we observe 15.2 +/- 4.4(stat)(-0.4)(+1.9)(syst) Xi(b)- candidates at a mass of 5.774 +/- 0.011(stat) +/- 0.015(syst) GeV. The significance of the observed signal is 5.5 sigma, equivalent to a probability of 3.3 x 10(-8) of it arising from a background fluctuation. Normalizing to the decay Lambda(b)-->J/psiLambda, we measure the relative rate sigma(Xi(b-) x B(Xi)b})- -->J/psiXi-)/sigma(Lambda(b)) x B(Lambda(b)-->J/psiLambda) = 0.28+/-0.09(stat)(-0.08)(+0.09)(syst).

We measure the charge asymmetry $A\equiv(N^{++} - N^{--})/(N^{++} + N^{--})$ of like-sign dimuon events in 6.1~fb$^{-1}$ of $p\bar{p}$ collisions recorded with the D0 detector at a center-of-mass energy $\sqrt{s}=1.96$~TeV at the Fermilab Tevatron collider. From $A$ we extract the like-sign dimuon charge asymmetry in semileptonic $b$-hadron decays: $\aslb=-0.00957\pm0.00251\thinspace({\rm stat})\pm0.00146\thinspace({\rm sys})$. It differs by 3.2~standard deviations from the standard model prediction $\aslb({\rm SM})=(-2.3^{+0.5}_{-0.6})\times10^{-4}$, and provides first evidence of anomalous $CP$ violation in the mixing of neutral $B$ mesons.

We present first evidence for the production of single top quarks in the D0 detector at the Fermilab Tevatron ppbar collider. The standard model predicts that the electroweak interaction can produce a top quark together with an antibottom quark or light quark, without the antiparticle top quark partner that is always produced from strong coupling processes. Top quarks were first observed in pair production in 1995, and since then, single top quark production has been searched for in ever larger datasets. In this analysis, we select events from a 0.9 fb-1 dataset that have an electron or muon and missing transverse energy from the decay of a W boson from the top quark decay, and two, three, or four jets, with one or two of the jets identified as originating from a b hadron decay. The selected events are mostly backgrounds such as W+jets and ttbar events, which we separate from the expected signals using three multivariate analysis techniques: boosted decision trees, Bayesian neural networks, and matrix element calculations. A binned likelihood fit of the signal cross section plus background to the data from the combination of the results from the three analysis methods gives a cross section for single top quark production of 4.7 +- 1.3 pb. The probability to measure a cross section at this value or higher in the absence of signal is 0.014%, corresponding to a 3.6 standard deviation significance. The measured cross section value is compatible at the 10% level with the standard model prediction for electroweak top quark production.

Algorithms distinguishing jets originating from b quarks from other jet flavors are important tools in the physics program of the D0 experiment at the Fermilab Tevatron p-pbar collider. This article describes the methods that have been used to identify b-quark jets, exploiting in particular the long lifetimes of b-flavored hadrons, and the calibration of the performance of these algorithms based on collider data.

We present the first measurement of dijet angular distributions in ppbar collisions at sqrt{s}=1.96TeV at the Fermilab Tevatron Collider. The measurement is based on a dataset corresponding to an integrated luminosity of up to 0.7fb-1 collected with the D0 detector. Dijet angular distributions have been measured over a range of dijet masses, from 0.25TeV to above 1.1TeV. The data are in good agreement with the predictions of perturbative QCD and are used to constrain new physics models including quark compositeness, large extra dimensions, and TeV-1 scale extra dimensions. For all models we set the most stringent direct limits to date.

We summarize and combine direct measurements of the mass of the W boson in √s=1.96 TeV proton-antiproton collision data collected by CDF and D0 experiments at the Fermilab Tevatron Collider. Earlier measurements from CDF and D0 are combined with the two latest, more precise measurements: a CDF measurement in the electron and muon channels using data corresponding to 2.2 fb−1 of integrated luminosity, and a D0 measurement in the electron channel using data corresponding to 4.3 fb−1 of integrated luminosity. The resulting Tevatron average for the mass of the W boson is MW=80387±16 MeV. Including measurements obtained in electron-positron collisions at LEP yields the most precise value of MW=80385±15 MeV.Received 29 July 2013DOI:https://doi.org/10.1103/PhysRevD.88.052018© 2013 American Physical Society

We present the results of a search for the flavor changing neutral current decay B_s^0->mu^+mu^- using 6.1 fb^-1 of ppbar collisions at sqrt(s) = 1.96 TeV collected by the D0 experiment at the Fermilab Tevatron Collider. The observed number of B_s^0 candidates is consistent with background expectations. The resulting upper limit on the branching fraction is BR(B_s^0->mu^+mu^-) < 5.1 x 10^-8 at the 95% C.L. This limit is a factor of 2.4 better than that of the previous D0 analysis and the best limit to date.

A fully reconstructed Bc-->J/psipi signal is observed with the D0 detector at the Fermilab Tevatron pp[over] collider using 1.3 fb(-1) of integrated luminosity. The signal consists of 54+/-12 candidates with a significance that exceeds 5 standard deviations, and confirms earlier observations of this decay. The measured mass of the Bc meson is 6300+/-14(stat)+/-5(syst) MeV/c2.

We present a measurement of the forward--backward asymmetry in top quark-antiquark production using the full Tevatron Run II dataset collected by the D0 experiment at Fermilab. The measurement is performed in lepton+jets final states using a new kinematic fitting algorithm for events with four or more jets and a new partial reconstruction algorithm for events with only three jets. Corrected for detector acceptance and resolution effects, the asymmetry is evaluated to be 10.6+-3.0 %. Results are consistent with the standard model predictions which range from 5.0% to 8.8%. We also present the dependence of the asymmetry on the invariant mass of the top quark--antiquark system and the difference in rapidities of top quark and antiquark.

We present an improved determination of the total width of the top quark, $Γ_t$, using 5.4 fb$^{-1}$ of integrated luminosity collected by the D0 Collaboration at the Tevatron $p\bar{p}$ Collider. The total width $Γ_t$ is extracted from the partial decay width $Γ(t\to Wb)$ and the branching fraction $\mathcal{B}(t\to Wb)$. $Γ(t\to Wb)$ is obtained from the $t$-channel single top quark production cross section and $\mathcal{B}(t\to Wb)$ is measured in $t\bar{t}$ events. For a top mass of $172.5\;\rm GeV$, the resulting width is $Γ_t = 2.00^{+0.47}_{-0.43}$ GeV. This translates to a top-quark lifetime of $τ_t = (3.29^{+0.90}_{-0.63})\times10^{-25}$ s. We also extract an improved direct limit on the CKM matrix element $0.81 &lt; |V_{tb}| \leq 1$ at 95% C.L. and a limit of $|V_{tb'}| &lt; 0.59$ for a high mass fourth generation bottom quark assuming unitarity of the fourth generation quark mixing matrix.

We present a measurement of the inclusive jet cross section using the Run II cone algorithm and data collected by the D0 experiment in p pbar collisions at a center-of-mass energy sqrt(s)=1.96 TeV, corresponding to an integrated luminosity of 0.70 fb^(-1). The jet energy calibration and the method used to extract the inclusive jet cross section are described. We discuss the main uncertainties, which are dominated by the jet energy scale uncertainty. The results cover jet transverse momenta from 50 GeV to 600 GeV with jet rapidities in the range -2.4 to 2.4 and are compared to predictions using recent proton parton distribution functions. Studies of correlations between systematic uncertainties in transverse momentum and rapidity are presented.

We present the observation of doubly-produced $J/\psi$ mesons with the D0 detector at Fermilab in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV. The production cross section for both singly and doubly-produced $J/\psi$ mesons is measured using a sample with an integrated luminosity of 8.1fb$^{-1}$. For the first time, the double $J/\psi$ production cross section is separated into contributions due to single and double parton scatterings. Using these measurements, we determine the effective cross section $\sigma_{eff}$, a parameter characterizing an effective spatial area of the parton-parton interactions and related to the parton spatial density inside the nucleon.

We report the first observation of single-top-quark production in the s channel through the combination of the CDF and D0 measurements of the cross section in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV. The data correspond to total integrated luminosities of up to 9.7 fb−1 per experiment. The measured cross section is σs=1.29+0.26−0.24 pb. The probability of observing a statistical fluctuation of the background to a cross section of the observed size or larger is 1.8×10−10, corresponding to a significance of 6.3 standard deviations for the presence of an s-channel contribution to the production of single-top quarks.Received 21 February 2014DOI:https://doi.org/10.1103/PhysRevLett.112.231803© 2014 American Physical Society

The random grid search (RGS) is a simple, but efficient, stochastic algorithm to find optimal cuts that was developed in the context of the search for the top quark at Fermilab in the mid-1990s. The algorithm, and associated code, have been enhanced recently with the introduction of two new cut types, one of which has been successfully used in searches for supersymmetry at the Large Hadron Collider. The RGS optimization algorithm is described along with the recent developments, which are illustrated with two examples from particle physics. One explores the optimization of the selection of vector boson fusion events in the four-lepton decay mode of the Higgs boson and the other optimizes SUSY searches using boosted objects and the razor variables. Program title: Random Grid Search Program Files doi: http://dx.doi.org/10.17632/mpcrnd7xb4.1 Licensing provisions: GNU General Public License 3 (GPL) Programming language: c++, python Nature of problem: We address the problem of scanning a large number of thresholds (cuts) on discriminating variables in order to find ones that maximize some measure of the degree of discrimination between classes of objects, for example, between signal and background events at the Large Hadron Collider (LHC). Solution method: The cuts searched are determined by the distribution of the objects that are the focus of an analysis. For example, if one is searching for supersymmetric events at the LHC, the cuts are determined by the predicted distribution of the variables that discriminate between the supersymmetric signal and the standard model background. In effect, we search for cuts using importance sampling determined by the signal distribution, thereby mitigating the curse of dimensionality. Additional comments including restrictions and unusual features: For cases with exceptionally large numbers of events, the program may take several hours to run. However, the system can be trivially parallelized, with no change to the program, by splitting large files into N smaller files and running the same set of cuts over the N files. The counts associated with each cut can then be summed over the N files.

We present the final combination of CDF and D0 measurements of cross sections for single-top-quark production in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV. The data correspond to total integrated luminosities of up to 9.7 fb^{-1} per experiment. The t-channel cross section is measured to be σ_{t}=2.25_{-0.31}^{+0.29} pb. We also present the combinations of the two-dimensional measurements of the s- vs t-channel cross section. In addition, we give the combination of the s+t channel cross section measurement resulting in σ_{s+t}=3.30_{-0.40}^{+0.52} pb, without assuming the standard model value for the ratio σ_{s}/σ_{t}. The resulting value of the magnitude of the top-to-bottom quark coupling is |V_{tb}|=1.02_{-0.05}^{+0.06}, corresponding to |V_{tb}|>0.92 at the 95% C.L.

We present measurements of the bb production cross section and angular correlations using the DØ detector at the Fermilab Tevatron pp Collider operating at s = 1.8 TeV. The b quark production cross section for |yb|<1.0 and pTb>6 GeV/c is extracted from single muon and dimuon data samples. The results agree in shape with the next-to-leading order QCD calculation of heavy flavor production but are greater than the central values of these predictions. The angular correlations between b and b quarks, measured from the azimuthal opening angle between their decay muons, also agree in shape with the next-to-leading order QCD prediction.

We present new results on the search for the top quark in p¯p collisions at √s=1.8 TeV with an integrated luminosity of 13.5±1.6 pb–1. We have considered t¯t production in the standard model using electron and muon dilepton decay channels ( t¯t→eμ+ jets, ee+ jets, and μμ+ jets) and single-lepton decay channels ( t¯t→e+ jets and μ+ jets) with and without tagging of b quark jets. From all channels we have nine events with an expected background of 3.8±0.9. If we assume that the excess is due to t¯t production, and assume a top mass of 180 GeV/ c2, we obtain a cross section of 8.2±5.1 pb.Received 7 November 1994DOI:https://doi.org/10.1103/PhysRevLett.74.2422©1995 American Physical Society

We present a search for events consistent with the production and decay of the squarks and gluinos of the minimal supersymmetric standard model (MSSM) in the D0 detector at the Fermilab Tevatron $p\overline{p}$ collider. We examined data for events containing large missing transverse energy and three or more jets. We observed no excess of events above the expected yield from standard model processes. For a choice of MSSM parameter values, we set a lower limit at the 95% confidence level on the mass of the gluino of 144 GeV ${/c}^{2}$ for all squark masses and a lower limit of 212 GeV ${/c}^{2}$ for equal squark and gluino masses.

We measure the top quark mass m t using t t pairs produced in the DØ detector by √ s = 1.8 TeV pp collisions in a 125 pb -1 exposure at the Fermilab Tevatron.We make a two constraint fit to m t in t t → bW + bW -final states with one W decaying to q q and the other to eν or µν.Events are binned in fit mass versus a measure of probability for events to be signal rather than background.Likelihood fits to the data yield m t = 173.3± 5.6 (stat) ± 6.2 (syst) GeV/c 2 .

We report a measurement of the inclusive muon and b-quark production cross sections in pp¯ collisions at s=1.8 TeV using the D0 detector at the Fermilab Tevatron collider. The inclusive muon spectrum extends over the kinematic range |yμ|<0.8 and 3.5<pTμ<60GeV/c, and is well described by the expected contributions from various known sources. The b-quark production cross section for |yb|<1.0 and pTb>6GeV/c is extracted, and agrees with next-to-leading order QCD predictions within the experimental and theoretical uncertainties.Received 12 December 1994DOI:https://doi.org/10.1103/PhysRevLett.74.3548©1995 American Physical Society

The cross section for the inclusive production of isolated photons has been measured in pp¯ collisions at s=1.96TeV with the DØ detector at the Fermilab Tevatron Collider. The photons span transverse momenta 23 to 300 GeV and have pseudorapidity |η|<0.9. The cross section is compared with the results from two next-to-leading order perturbative QCD calculations. The theoretical predictions agree with the measurement within uncertainties.

We present a measurement of the inclusive jet cross section in p¯p collisions at √s =1.8 TeV at the Fermilab Tevatron using the Collider Detector at Fermilab. Good agreement is seen with the predictions of recent next-to-leading-order [O(α3s)] QCD predictions. The dependence of the cross section on clustering cone size is reported for the first time. An improved limit on Λc, a term characterizing possible quark substructure, is set at 1.4 TeV (95% C.L.).Received 7 August 1991DOI:https://doi.org/10.1103/PhysRevLett.68.1104©1992 American Physical Society

Correlations in the azimuthal angle between the two largest transverse momentum jets have been measured using the D0 detector in $p\overline{p}$ collisions at a center-of-mass energy $\sqrt{s}=1.96\text{ }\text{ }\mathrm{TeV}$. The analysis is based on an inclusive dijet event sample in the central rapidity region corresponding to an integrated luminosity of $150\text{ }\text{ }{\mathrm{pb}}^{\ensuremath{-}1}$. Azimuthal correlations are stronger at larger transverse momenta. These are well described in perturbative QCD at next-to-leading order in the strong coupling constant, except at large azimuthal differences where contributions with low transverse momentum are significant.

We report the observation of the doubly strange b baryon Omegab- in the decay channel Omegab(-)-->J/psiOmega-, with J/psi-->mu+mu(-) and Omega(-)-->LambdaK(-)-->(ppi-)K-, in pp collisions at sqrt[s]=1.96 TeV. Using approximately 1.3 fb(-1) of data collected with the D0 detector at the Fermilab Tevatron Collider, we observe 17.8+/-4.9(stat)+/-0.8(syst) Omegab- signal events at a mass of 6.165+/-0.010(stat)+/-0.013(syst) GeV. The significance of the observed signal is 5.4sigma, corresponding to a probability of 6.7 x 10(-8) of it arising from a background fluctuation.

We present a measurement of the W boson mass in W-->e(nu) decays using 1 fb-1 of data collected with the D0 detector during Run II of the Fermilab Tevatron collider. With a sample of 499830 W-->e(nu) candidate events, we measure M(W)=80.401+/-0.043 GeV. This is the most precise measurement from a single experiment.

We report the direct observation of the excited $L=1$ state ${B}_{s2}^{*}$ in fully reconstructed decays to ${B}^{+}{K}^{\ensuremath{-}}$. The mass of the ${B}_{s2}^{*}$ meson is measured to be $5839.6\ifmmode\pm\else\textpm\fi{}1.1(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.7(\mathrm{syst})\text{ }\text{ }\mathrm{MeV}/{c}^{2}$, and its production rate relative to the ${B}^{+}$ meson is measured to be $[1.15\ifmmode\pm\else\textpm\fi{}0.23(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.13(\mathrm{syst})]%$.

We present a measurement of the muon charge asymmetry from W boson decays using 0.3 fb−1 of data collected at s=1.96 GeV between 2002 and 2004 with the D0 detector at the Fermilab Tevatron pp¯ Collider. We compare our findings with expectations from next-to-leading-order calculations performed using the CTEQ6.1M and MRST04 NLO parton distribution functions. Our findings can be used to constrain future parton distribution function fits.Received 27 September 2007DOI:https://doi.org/10.1103/PhysRevD.77.011106©2008 American Physical Society

We report the results of a search for a heavy neutral gauge boson Z′ decaying into the dielectron final state using data corresponding to an integrated luminosity of 5.4 fb−1 collected by the D0 experiment at the Fermilab Tevatron Collider. No significant excess above the standard model prediction is observed in the dielectron invariant-mass spectrum. We set 95σ(pp¯→Z′)×BR(Z′→ee) depending on the dielectron invariant mass. These cross section limits are used to determine lower mass limits for Z′ bosons in a variety of models. For the sequential standard model Z′ boson a lower mass limit of 1023 GeV is obtained.

We use higher-order quantum chromodynamics calculations to extract the mass of the top quark from the ttbar cross section measured in the lepton+jets channel in ppbar collisions at sqrt(s)=1.96 TeV using 5.3 fb-1 of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron Collider. The extracted top quark pole mass and MSbar mass are compared to the current Tevatron average top quark mass obtained from direct measurements.

We determine the strong coupling constant ${\ensuremath{\alpha}}_{s}$ and its energy dependence from the ${p}_{T}$ dependence of the inclusive jet cross section in $p\overline{p}$ collisions at $\sqrt{s}=1.96\text{ }\text{ }\mathrm{TeV}$. The strong coupling constant is determined over the transverse momentum range $50&lt;{p}_{T}&lt;145\text{ }\text{ }\mathrm{GeV}$. Using perturbative QCD calculations to order $\mathcal{O}({\ensuremath{\alpha}}_{s}^{3})$ combined with $\mathcal{O}({\ensuremath{\alpha}}_{s}^{4})$ contributions from threshold corrections, we obtain ${\ensuremath{\alpha}}_{s}({M}_{Z})={0.1161}_{\ensuremath{-}0.0048}^{+0.0041}$. This is the most precise result obtained at a hadron-hadron collider.

We present a model-independent measurement of $t$-channel electroweak production of single top quarks in $\ppbar$ collisions at $\sqrt{s}=1.96\;\rm TeV$. Using $5.4\;\rm fb^{-1}$ of integrated luminosity collected by the D0 detector at the Fermilab Tevatron Collider, and selecting events containing an isolated electron or muon, missing transverse energy and one or two jets originating from the fragmentation of $b$ quarks, we measure a cross section $\sigma({\ppbar}{\rargap}tqb+X) = 2.90 \pm 0.59\;\rm (stat+syst)\; pb$ for a top quark mass of $172.5\;\rm GeV$. The probability of the background to fluctuate and produce a signal as large as the one observed is $1.6\times10^{-8}$, corresponding to a significance of 5.5 standard deviations.

We present a measurement of the inclusive top quark pair production cross section in \ppbar collisions at (\sqrt{s}=1.96) TeV utilizing data corresponding to an integrated luminosity of \lumi\ collected with the D0 detector at the Fermilab Tevatron Collider. We consider final states containing one high-$p_{T}$ isolated electron or muon and at least two jets, and we perform three analyses: one exploiting specific kinematic features of \ttbar events, the second using $b$-jet identification, and the third using both techniques to separate \ttbar\ signal from background. In the third case, we determine simultaneously the $t\bar{t}$ cross section and the ratio of the production rates of $W$+heavy flavor jets and $W$+light flavor jets, which reduces the impact of the systematic uncertainties related to the background estimation. Assuming a top quark mass of 172.5 GeV, we obtain $\sigma_{t\bar{t}} = 7.78^{+0.77}_{-0.64} $ pb. This result agrees with predictions of the standard model.

Each generation of high-energy physics experiments is grander in scale than the previous—more powerful, more complex, and more demanding in terms of data handling and analysis. The spectacular performance of the Tevatron and the beginning of operations at the Large Hadron Collider have placed us at the threshold of a new era in particle physics. The discovery of the Higgs boson, or another agent of electroweak symmetry breaking, and evidence of new physics may be just around the corner. The greatest challenge in these pursuits is to extract the extremely rare signals, if any, from the huge backgrounds that arise from known physics processes. The use of advanced analysis techniques is crucial in achieving this goal. In this review, I discuss the concepts of optimal analysis, some important advanced analysis methods, and a few examples. The judicious use of these advanced methods should enable new discoveries and produce results with better precision, robustness, and clarity.

We present a measurement of the ratio of events with correlated t and tbar spins to the total number of ttbar events. This ratio f is evaluated using a matrix-element-based approach in events with a single lepton (electron or muon) and at least four jets. We analyze ppbar collisions data corresponding to an integrated luminosity of 5.3 fb^-1 collected with the D0 detector at the Fermilab Tevatron collider operating at a center of mass energy $\sqrt{s}=1.96$ TeV. Combining this result with a recent measurement of f in dilepton final states, we find f in agreement with the standard model. In addition, the combination provides evidence for the presence of spin correlation in ttbar events with a significance of more than three standard deviations.

We present a measurement of the electron charge asymmetry in $p\bar{p}\rightarrow W+X \rightarrow e\nu +X$ events at a center-of-mass energy of 1.96 TeV, using data corresponding to 9.7~fb$^{-1}$ of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider. The asymmetry is measured as a function of the electron pseudorapidity and is presented in five kinematic bins based on the electron transverse energy and the missing transverse energy in the event. The measured asymmetry is compared with next-to-leading-order predictions in perturbative quantum chromodynamics and provides accurate information for the determination of parton distribution functions of the proton. This is the most precise lepton charge asymmetry measurement to date.

We measure the inclusive single muon charge asymmetry and the like-sign dimuon charge asymmetry in pp collisions using the full data set of 10.4 fb -1 collected with

We report evidence for the simultaneous production of $J/\psi$ and $\Upsilon$ mesons in 8.1 fb$^{-1}$ of data collected at $\sqrt{s}=$1.96 TeV by the D0 experiment at the Fermilab $p \bar p$ Tevatron Collider. Events with these characteristics are expected to be produced predominantly by gluon-gluon interactions. In this analysis, we extract the effective cross section characterizing the initial parton spatial distribution, $\sigma_{eff}=2.2\pm 0.7\mbox{(stat)} \pm 0.9 \mbox{(syst)} ~\mbox{mb}$.

Drell-Yan lepton pairs produced in the process $p\overline{p}\ensuremath{\rightarrow}{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}+X$ through an intermediate ${\ensuremath{\gamma}}^{*}/Z$ boson have an asymmetry in their angular distribution related to the spontaneous symmetry breaking of the electroweak force and the associated mixing of its neutral gauge bosons. The CDF and D0 experiments have measured the effective-leptonic electroweak mixing parameter ${\mathrm{sin}}^{2}{\ensuremath{\theta}}_{\mathrm{eff}}^{\mathrm{lept}}$ using electron and muon pairs selected from the full Tevatron proton-antiproton data sets collected in 2001-2011, corresponding to $9--10\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of integrated luminosity. The combination of these measurements yields the most precise result from hadron colliders, ${\mathrm{sin}}^{2}{\ensuremath{\theta}}_{\mathrm{eff}}^{\mathrm{lept}}=0.23148\ifmmode\pm\else\textpm\fi{}0.00033$. This result is consistent with, and approaches in precision, the best measurements from electron-positron colliders. The standard model inference of the on-shell electroweak mixing parameter ${\mathrm{sin}}^{2}{\ensuremath{\theta}}_{W}$, or equivalently the $W$-boson mass ${M}_{W}$, using the zfitter software package yields ${\mathrm{sin}}^{2}{\ensuremath{\theta}}_{W}=0.22324\ifmmode\pm\else\textpm\fi{}0.00033$ or equivalently, ${M}_{W}=80.367\ifmmode\pm\else\textpm\fi{}0.017\text{ }\text{ }\mathrm{GeV}/{c}^{2}$.

The International Linear Collider (ILC) is on the table now as a new global energy-frontier accelerator laboratory taking data in the 2030s. The ILC addresses key questions for our current understanding of particle physics. It is based on a proven accelerator technology. Its experiments will challenge the Standard Model of particle physics and will provide a new window to look beyond it. This document brings the story of the ILC up to date, emphasizing its strong physics motivation, its readiness for construction, and the opportunity it presents to the US and the global particle physics community.

We present a search for charged Higgs bosons in decays of pair-produced top quarks using $109.2\ifmmode\pm\else\textpm\fi{}5.8{\mathrm{pb}}^{\ensuremath{-}1}$ of data recorded from $p\overline{p}$ collisions at $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8\mathrm{TeV}$ by the D0 detector during 1992--1996 at the Fermilab Tevatron. No evidence is found for charged Higgs production, and most parts of the $[{M}_{{H}^{+}},\mathrm{tan}\ensuremath{\beta}]$ parameter space where the decay $t\ensuremath{\rightarrow}{H}^{+}b$ has a branching fraction close to or larger than that for $t\ensuremath{\rightarrow}{W}^{+}b$ are excluded at $95%$ confidence level. Assuming ${m}_{t}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}175\mathrm{GeV}$ and $\ensuremath{\sigma}(p\overline{p}\ensuremath{\rightarrow}t\overline{t})\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}5.5\mathrm{pb}$, for ${M}_{{H}^{+}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}60\mathrm{GeV}$, we exclude $\mathrm{tan}\ensuremath{\beta}&lt;0.97$ and $\mathrm{tan}\ensuremath{\beta}&gt;40.9$.

We report a measurement of the top quark mass using six candidate events for the process $p\overline{p}\ensuremath{\rightarrow}t\overline{t}+\stackrel{\ensuremath{\rightarrow}}{X}{l}^{+}\ensuremath{\nu}{\mathrm{bl}}^{\ensuremath{-}}\overline{\ensuremath{\nu}}\overline{b}+X$, observed in the D0 experiment at the Fermilab $p\overline{p}$ collider. Using maximum likelihood fits to the dynamics of the decays, we measure a mass for the top quark of ${m}_{t}=168.4\ifmmode\pm\else\textpm\fi{}12.3(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}3.6(\mathrm{syst}) \mathrm{Gev}$. We combine this result with our previous measurement in the $t\overline{t}\ensuremath{\rightarrow}l+\mathrm{jets}$ channel to obtain ${m}_{t}=172.1\ifmmode\pm\else\textpm\fi{}7.1 \mathrm{GeV}$ as the best value of the mass of the top quark measured by D0.

We present a search for pair produced top squarks, the supersymmetric partners of the top quark, using the D0 detector at the Fermilab Tevatron $p\overline{p}$ collider. We consider a scenario in which the lighter of the two top squarks ${\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{t}}_{1}$ decays with 100% branching fraction to a charm quark and the lightest neutralino ${\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\chi}}}_{1}^{0}$ yielding a signal of two acollinear jets with missing transverse energy. We observe 3 events while we expect $3.5\ifmmode\pm\else\textpm\fi{}1.2$ events from the known standard model processes. We exclude at the 95% confidence level a significant region of the ${m}_{{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{t}}_{1}}$- ${m}_{{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\chi}}}_{1}^{0}}$ parameter space. The highest ${m}_{{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{t}}_{1}}$ value we exclude is $93\mathrm{GeV}{/c}^{2}$ with a corresponding ${m}_{{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\chi}}}_{1}^{0}}$ value of $8\mathrm{G}\mathrm{e}\mathrm{V}/{c}^{2}$.

We report a new measurement of the pseudorapidity (eta) and transverse-energy ( E(T)) dependence of the inclusive jet production cross section in pp(macro) collisions at square root of s = 1.8 TeV using 95 pb(-1) of data collected with the D0 detector at the Fermilab Tevatron. The differential cross section d(2)sigma/(dE(T)d eta) is presented up to eta = 3, significantly extending previous measurements. The results are in good overall agreement with next-to-leading order predictions from QCD and indicate a preference for certain parton distribution functions.

We present results on the search for the top quark in pp\ifmmode\bar\else\textasciimacron\fi{} collisions at \ensuremath{\surd}s =1.8 TeV with an integrated luminosity of 13.5\ifmmode\pm\else\textpm\fi{}1.6 ${\mathrm{pb}}^{\mathrm{\ensuremath{-}}1}$. We have considered tt\ifmmode\bar\else\textasciimacron\fi{} production in the standard model using electron and muon dilepton decay channels (tt\ifmmode\bar\else\textasciimacron\fi{}\ensuremath{\rightarrow}e\ensuremath{\mu}+jets, ee+jets, and \ensuremath{\mu}\ensuremath{\mu}+jets) and single-lepton decay channels (tt\ifmmode\bar\else\textasciimacron\fi{}\ensuremath{\rightarrow}e+jets and \ensuremath{\mu}+jets) with and without tagging of b quark jets. An analysis of these data optimized for top quark masses below 140 GeV/${\mathit{c}}^{2}$ gives a lower top quark mass limit of 128 GeV/${\mathit{c}}^{2}$. An analysis optimized for higher top quark masses yields 9 events with an expected background of 3.8\ifmmode\pm\else\textpm\fi{}0.9. If we assume that the excess is due to tt\ifmmode\bar\else\textasciimacron\fi{} production, and assuming a top quark mass of 180 GeV/${\mathit{c}}^{2}$, we obtain a cross section of 8.2\ifmmode\pm\else\textpm\fi{}5.1 pb.

We report a new measurement of the cross section for the production of isolated photons with transverse energies ( E(gamma)(T)) above 10 GeV and pseudorapidities |eta|<2.5 in p&pmacr; collisions at sqrt[s] = 1.8 TeV. The results are based on a data sample of 107.6 pb(-1) recorded during 1992-1995 with the D0 detector at the Fermilab Tevatron collider. The background, predominantly from jets which fragment to neutral mesons, was estimated using the longitudinal shower shape of photon candidates in the calorimeter. The measured cross section is in good agreement with the next-to-leading order QCD calculation for E(gamma)(T) greater, similar36 GeV.

A search for pair production of doubly-charged Higgs bosons in the process p pbar to H++H-- to mu+mu+mu-mu- is performed with the D0 Run II detector at the Fermilab Tevatron. The analysis is based on a sample of inclusive di-muon data collected at an energy of sqrt{s}=1.96 TeV, corresponding to an integrated luminosity of 113 pb-1. In the absence of a signal, 95 % confidence level mass limits of M(H++L)>118.4 GeV/c2 and M(H++R)>98.2 GeV/c2 are set for left-handed and right-handed doubly-charged Higgs bosons, respectively, assuming 100% branching into muon pairs.

We present a measurement of the electron charge asymmetry in pp[over ]-->W+X-->enu+X events at a center of mass energy of 1.96 TeV using 0.75 fb(-1) of data collected with the D0 detector at the Fermilab Tevatron Collider. The asymmetry is measured as a function of the electron transverse momentum and pseudorapidity in the interval (-3.2, 3.2) and is compared with expectations from next-to-leading order calculations in perturbative quantum chromodynamics. These measurements will allow more accurate determinations of the proton parton distribution functions.

We present new measurements of differential cross sections for Z/γ∗(→μμ)+jet+X production in a 1 fb−1 data sample collected with the DØ detector in pp¯ collisions at s=1.96TeV. Results include the first measurements differential in the Z/γ∗ transverse momentum and rapidity, as well as new measurements differential in the leading jet transverse momentum and rapidity. Next-to-leading order perturbative QCD predictions are compared to the measurements, and reasonable agreement is observed, except in the region of low Z/γ∗ transverse momentum. Predictions from two event generators based on matrix elements and parton showers, and one pure parton shower event generator are also compared to the measurements. These show significant overall normalization differences to the data and have varied success in describing the shape of the distributions.

This Letter presents the first strong evidence for the resolution of the excited $B$ mesons ${B}_{1}$ and ${B}_{2}^{*}$ as two separate states in fully reconstructed decays to ${B}^{+(*)}{\ensuremath{\pi}}^{\ensuremath{-}}$. The mass of ${B}_{1}$ is measured to be $5720.6\ifmmode\pm\else\textpm\fi{}2.4\ifmmode\pm\else\textpm\fi{}1.4\text{ }\text{ }\mathrm{MeV}/{c}^{2}$ and the mass difference $\ensuremath{\Delta}M$ between ${B}_{2}^{*}$ and ${B}_{1}$ is $26.2\ifmmode\pm\else\textpm\fi{}3.1\ifmmode\pm\else\textpm\fi{}0.9\text{ }\text{ }\mathrm{MeV}/{c}^{2}$, giving the mass of the ${B}_{2}^{*}$ as $5746.8\ifmmode\pm\else\textpm\fi{}2.4\ifmmode\pm\else\textpm\fi{}1.7\text{ }\text{ }\mathrm{MeV}/{c}^{2}$. The production rate for ${B}_{1}$ and ${B}_{2}^{*}$ mesons is determined to be a fraction $(13.9\ifmmode\pm\else\textpm\fi{}1.9\ifmmode\pm\else\textpm\fi{}3.2)%$ of the production rate of the ${B}^{+}$ meson.

Using approximately 1.3 fb(-1) of data collected by the D0 detector between 2002 and 2006, we measure the lifetime of the Bc+/- meson in the Bc-/+-->J/psimicro+/-+X final state. A simultaneous unbinned likelihood fit to the J/psi+micro invariant mass and lifetime distributions yields a signal of 881+/-80(stat) candidates and a lifetime measurement of tau(Bc+/-)=0.448(-0.036)(+0.038)(stat)+/-0.032(syst) ps.

We present a search for the pair production of scalar top quarks, t˜, using 995 pb−1 of data collected in pp¯ collisions with the DØ detector at the Fermilab Tevatron Collider at s=1.96TeV. Both scalar top quarks are assumed to decay into a charm quark and a neutralino (χ˜10), where χ˜10 is the lightest supersymmetric particle. This leads to a final state with two acoplanar charm jets and missing transverse energy. We find the yield of such events to be consistent with the standard model expectation, and exclude sets of t˜ and χ˜10 masses at the 95% C.L. that substantially extend the domain excluded by previous searches.

We present a measurement of direct photon pair production cross sections using 4.2 fb-1 of data collected with the D0 detector at the Fermilab Tevatron proton-antiproton Collider. We measure single differential cross sections as a function of the diphoton mass, the transverse momentum of the diphoton system, the azimuthal angle between the photons, and the polar scattering angle of the photons, as well as the double differential cross sections considering the last three kinematic variables in three diphoton mass bins. The results are compared with different perturbative QCD predictions and event generators.

We present a study of the polarization of the Υ(1S) and Υ(2S) states using a 1.3 fb−1 data sample collected by the D0 experiment in 2002–2006 during run II of the Fermilab Tevatron Collider. We measure the polarization parameter α=(σT−2σL)/(σT+2σL), where σT and σL are the transversely and longitudinally polarized components of the production cross section, as a function of the transverse momentum (pΥT) for the Υ(1S) and Υ(2S). Significant pΥT-dependent longitudinal polarization is observed for the Υ(1S). A comparison with theoretical models is presented.Received 18 April 2008DOI:https://doi.org/10.1103/PhysRevLett.101.182004©2008 American Physical Society

We search for long-lived charged massive particles using $1.1\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of data collected by the D0 detector at the Fermilab Tevatron $p\overline{p}$ Collider. Time-of-flight information is used to search for pair produced long-lived tau sleptons, gauginolike charginos, and Higgsino-like charginos. We find no evidence of a signal and set 95% C.L. cross section upper limits for staus, which vary from 0.31 to 0.04 pb for stau masses between 60 and 300 GeV. We also set lower mass limits of 206 GeV (171 GeV) for pair produced charged gauginos (Higgsinos).

The D0 Collaboration reports direct evidence for electroweak production of single top quarks through the t-channel exchange of a virtual W boson. This is the first analysis to isolate an individual single top quark production channel. We select events containing an isolated electron or muon, missing transverse energy, and two, three or four jets from 2.3 fb−1 of pp¯ collisions at the Fermilab Tevatron Collider. One or two of the jets are identified as containing a b hadron. We combine three multivariate techniques optimized for the t-channel process to measure the t- and s-channel cross sections simultaneously. We measure cross sections of 3.14−0.80+0.94pb for the t-channel and 1.05±0.81pb for the s-channel. The measured t-channel result is found to have a significance of 4.8 standard deviations and is consistent with the standard model prediction.

We report on a first search for production of the lightest neutral $CP$-even Higgs boson ($h$) in the next-to-minimal supersymmetric standard model, where $h$ decays to a pair of neutral pseudoscalar Higgs bosons ($a$), using $4.2\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of data recorded with the D0 detector at Fermilab. The $a$ bosons are required to either both decay to ${\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ or one to ${\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ and the other to ${\ensuremath{\tau}}^{+}{\ensuremath{\tau}}^{\ensuremath{-}}$. No significant signal is observed, and we set limits on its production as functions of ${M}_{a}$ and ${M}_{h}$.

We present a search for flavor changing neutral currents via quark-gluon couplings in a sample of single top quark final states corresponding to 2.3 fb^-1 of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider. We select events containing a single top quark candidates with an additional jet, and obtain separation between signal and background using Bayesian neural networks. We find consistency between background expectation and observed data, and set limits on flavor changing neutral current gluon couplings of the top quark to up quarks (tgu) and charm quarks (tgc). The cross section limits at the 95% C.L. are sigma_tgu<0.20pb and sigma_tgc<0.27pb. These correspond to limits on the top quark decay branching fractions of B(t->gu)<2.0*10^-4 and B(t->gc)<3.9*10^-3.

We present a new measurement of the Z/γ∗ transverse momentum distribution in the range 0–330 GeV, in proton–antiproton collisions at s=1.96TeV. The measurement uses 0.97 fb−1 of integrated luminosity recorded by the D0 experiment and is the first using the Z/γ∗→μ+μ−+X channel at this center-of-mass energy. This is also the first measurement of the Z/γ∗ transverse momentum distribution that presents the result at the level of particles entering the detector, minimizing dependence on theoretical models. As any momentum of the Z/γ∗ in the plane transverse to the incoming beams must be balanced by some recoiling system, primarily the result of QCD radiation in the initial state, this variable is an excellent probe of the underlying process. Tests of the predictions of QCD calculations and current event generators show they have varied success in describing the data. Using this measurement as an input to theoretical predictions will allow for a better description of hadron collider data and hence it will increase experimental sensitivity to rare signals.

We present a search for the production of a heavy gauge boson, W′, that decays to third-generation quarks, by D0 Collaboration in pp¯ collisions at s=1.96TeV. We set 95% confidence level upper limits on the production cross section times branching fraction. For the first time, we set limits for arbitrary combinations of left- and right-handed couplings of the W′ boson to fermions. For couplings with the same strength as for the standard model W boson, we set the following limits, assuming that there are right-handed neutrinos νR for all three generations with M(W′)>m(νR): M(W′)>863GeV for purely left-handed couplings, M(W′)>885GeV for purely right-handed couplings, and M(W′)>916GeV if both left- and right-handed couplings are present. The limit for right-handed couplings improves for M(W′)<m(νR) to M(W′)>890GeV.

We present a measurement of the ratio of top quark branching fractions R = B(t -> Wb)/B(t -> Wq), where q can be a d, s or b quark, in the lepton+jets and dilepton ttbar final states. The measurement uses data from 5.4 fb-1 of ppbar collisions collected with the D0 detector at the Fermilab Tevatron Collider. We measure R = 0.90 +/- 0.04, and we extract the CKM matrix element |Vtb| as |Vtb| = 0.95 +/- 0.02, assuming unitarity of the 3x3 CKM matrix.

We present a measurement of the average value of a new observable at hadron colliders that is sensitive to QCD dynamics and to the strong coupling constant, while being only weakly sensitive to parton distribution functions. The observable measures the angular correlations of jets and is defined as the number of neighboring jets above a given transverse momentum threshold which accompany a given jet within a given distance Delta-R in the plane of rapidity and azimuthal angle. The ensemble average over all jets in an inclusive jet sample is measured and the results are presented as a function of transverse momentum of the inclusive jets, in different regions of Delta-R and for different transverse momentum requirements for the neighboring jets. The measurement is based on a data set corresponding to an integrated luminosity of 0.7 fb-1 collected with the D0 detector at the Fermilab Tevatron Collider in pp-bar collisions at sqrt(s)=1.96 The results are well described by a perturbative QCD calculation in next-to-leading order in the strong coupling constant, corrected for non-perturbative effects. From these results, we extract the strong coupling and test the QCD predictions for its running over a range of momentum transfers of 50-400 GeV.

We report the combination of recent measurements of the helicity of the $W$ boson from top quark decay by the CDF and D0 collaborations, based on data samples corresponding to integrated luminosities of $2.7--5.4\text{ }\text{ }\mathrm{f}{\mathrm{b}}^{\ensuremath{-}1}$ of $p\overline{p}$ collisions collected during Run II of the Fermilab Tevatron collider. Combining measurements that simultaneously determine the fractions of $W$ bosons with longitudinal (${f}_{0}$) and right-handed (${f}_{+}$) helicities, we find ${f}_{0}=0.722\ifmmode\pm\else\textpm\fi{}0.081[\ifmmode\pm\else\textpm\fi{}0.062(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.052(\mathrm{syst})]$ and ${f}_{+}=\ensuremath{-}0.033\ifmmode\pm\else\textpm\fi{}0.046[\ifmmode\pm\else\textpm\fi{}0.034(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.031(\mathrm{syst})]$. Combining measurements where one of the helicity fractions is fixed to the value expected in the standard model, we find ${f}_{0}=0.682\ifmmode\pm\else\textpm\fi{}0.057[\ifmmode\pm\else\textpm\fi{}0.035(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.046(\mathrm{syst})]$ for fixed ${f}_{+}$ and ${f}_{+}=\ensuremath{-}0.015\ifmmode\pm\else\textpm\fi{}0.035[\ifmmode\pm\else\textpm\fi{}0.018(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.030(\mathrm{syst})]$ for fixed ${f}_{0}$. The results are consistent with standard model expectations.

Using data corresponding to an integrated luminosity of 1.3 fb^-1, we observe a narrow mass state decaying into Upsilon(1S)+gamma, where the Upsilon(1S) meson is detected by its decay into a pair of oppositely charged muons, and the photon is identified through its conversion into an electron-positron pair. The significance of this observation is 5.6 standard deviations. The mass of the state is centered at 10.551 \pm 0.014 (stat.) \pm 0.017 (syst.) GeV/c^2, which is consistent with that of the state recently observed by the ATLAS Collaboration.

We present a measurement of the time-integrated flavor-specific semileptonic charge asymmetry in the decays of ${B}_{s}^{0}$ mesons that have undergone flavor mixing, ${a}_{\mathrm{sl}}^{s}$, using ${B}_{s}^{0}({\overline{B}}_{s}^{0})\ensuremath{\rightarrow}{D}_{s}^{\ensuremath{\mp}}{\ensuremath{\mu}}^{\ifmmode\pm\else\textpm\fi{}}X$ decays, with ${D}_{s}^{\ensuremath{\mp}}\ensuremath{\rightarrow}\ensuremath{\phi}{\ensuremath{\pi}}^{\ensuremath{\mp}}$ and $\ensuremath{\phi}\ensuremath{\rightarrow}{K}^{+}{K}^{\ensuremath{-}}$, using $10.4\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of proton-antiproton collisions collected by the D0 detector during Run II at the Fermilab Tevatron Collider. A fit to the difference between the time-integrated ${D}_{s}^{\ensuremath{-}}$ and ${D}_{s}^{+}$ mass distributions of the ${B}_{s}^{0}$ and ${\overline{B}}_{s}^{0}$ candidates yields the flavor-specific asymmetry ${a}_{\mathrm{sl}}^{s}=[\ensuremath{-}1.12\ifmmode\pm\else\textpm\fi{}0.74(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.17(\mathrm{syst})]%$, which is the most precise measurement and in agreement with the standard model prediction.

We present measurements of lepton ($\ensuremath{\ell}$) angular distributions in top-quark ($t$) pair production and $t\overline{t}\ensuremath{\rightarrow}{W}^{+}b{W}^{\ensuremath{-}}\overline{b}\ensuremath{\rightarrow}{\ensuremath{\ell}}^{+}\ensuremath{\nu}b{\ensuremath{\ell}}^{\ensuremath{-}}\overline{\ensuremath{\nu}}\overline{b}$ decays produced in $p\overline{p}$ collisions at a center-of-mass energy of $\sqrt{s}=1.96\text{ }\text{ }\mathrm{TeV}$, where $\ensuremath{\ell}$ is an electron or muon. Using data corresponding to an integrated luminosity of $5.4\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$, collected with the D0 detector at the Fermilab Tevatron Collider, we measure for the first time the leptonic forward-backward asymmetry in dilepton final states and obtain ${A}_{\mathrm{FB}}^{\ensuremath{\ell}}=(5.8\ifmmode\pm\else\textpm\fi{}5.1(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}1.3(\mathrm{syst}))%$, corrected for detector acceptance. This is compared to the standard model prediction of ${A}_{\mathrm{FB}}^{\ensuremath{\ell}}(\mathrm{predicted})=(4.7\ifmmode\pm\else\textpm\fi{}0.1)%$. A deviation from the standard model prediction as previously seen in a D0 measurement based on the analysis of the $\ensuremath{\ell}+\mathrm{\text{jets}}$ final state is not observed in these dilepton final states. The two results differ from each other by 1.4 standard deviations and are combined to obtain ${A}_{\mathrm{FB}}^{\ensuremath{\ell}}=(11.8\ifmmode\pm\else\textpm\fi{}3.2)%$. Furthermore, we present a first study of the top-quark polarization.

We determine the fraction of events with double parton (DP) scattering in a single ppbar collision at sqrt{s}=1.96 TeV in samples of photon + 3 jet and photon + b/c jet + 2 jet events collected with the D0 detector and corresponding to an integrated luminosity of about 8.7 fb^{-1}. The DP fractions and effective cross sections (sigma_eff) are measured for both event samples using the same kinematic selections. The measured DP fractions range from 0.21 to 0.17, with effective cross sections in the photon + 3 jet and photon + b/c jet + 2 jet samples of sigma_eff^incl = 12.7 +- 0.2 (stat) +- 1.3 (syst) mb and sigma_eff^HF = 14.6 +- 0.6 (stat) +- 3.2 (syst) mb, respectively.

We present a study of the inclusive production of the X(4140) state with the decay to the J/ψϕ final state in hadronic collisions. Based on 10.4 fb^{-1} of pp[over ¯] collision data collected by the D0 experiment at the Fermilab Tevatron collider, we report the first evidence for the prompt production of an X(4140) state and find the fraction of X(4140) events originating from b hadrons to be f_{b}=0.39±0.07(stat)±0.10(syst). The ratio of the nonprompt X(4140) production rate to the B_{s}^{0} yield in the same channel is R=0.19±0.05(stat)±0.07(syst). The values of the mass M=4152.5±1.7(stat)_{-5.4}^{+6.2}(syst) MeV and width Γ=16.3±5.6(stat)±11.4(syst) MeV are consistent with previous measurements.

We present measurements of the cross sections for the two main production modes of single top quarks in $p\bar{p}$ collisions at $\sqrt{s} = 1.96$ TeV in the Run II data collected with the D0 detector at the Fermilab Tevatron Collider, corresponding to an integrated luminosity of 9.7 fb$^{-1}$. The s-channel cross section is measured to be $σ(p\bar{p} \to tb+X) = 1.10^{+0.33}_{-0.31}$ pb with no assumptions on the value of the t-channel cross section. Similarly, the t-channel cross section is measured to be $σ(p\bar{p} \to tqb+X) = 3.07^{+0.54}_{-0.49}$ pb. We also measure the $s+t$ combined cross section as $σ(p\bar{p} \to tb+X, tqb+X) = 4.11^{+0.60}_{-0.55}$ pb and set a lower limit on the CKM matrix element $|V_{tb}| &gt; 0.92$ at $95\%$ C.L., assuming $m_t=172.5$ GeV. The probability to measure a cross section for the s channel at the observed value or higher in the absence of signal is $1.0\times 10^{-4}$, corresponding to a significance of 3.7 standard deviations.

We present measurements of asymmetries in angular distributions of leptons produced in $t\overline{t}$ events in proton-antiproton collisions at the Fermilab Tevatron Collider. We consider final states where the ${W}^{\ifmmode\pm\else\textpm\fi{}}$ bosons from top quark and antiquark decays both decay into $\ensuremath{\ell}\ensuremath{\nu}$ ($\ensuremath{\ell}=e$, $\ensuremath{\mu}$) resulting in oppositely charged dilepton final states with accompanying jets. Using $9.7\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of integrated luminosity collected with the D0 detector, we find the asymmetries in lepton pseudorapidity compatible with predictions based on the standard model.

The production of top quark-antiquark pair events in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV is studied as a function of the transverse momentum and absolute value of the rapidity of the top quarks as well as of the invariant mass of the $t\bar{t}$ pair. We select events containing an isolated lepton, a large imbalance in transverse momentum, and four or more jets with at least one jet identified to originate from a $b$ quark. The data sample corresponds to 9.7 fb$^{-1}$ of integrated luminosity recorded with the D0 detector during Run II of the Fermilab Tevatron Collider. Observed differential cross sections are consistent with standard model predictions.

Abstract C 3 is an opportunity to realize an e + e - collider for the study of the Higgs boson at √ s = 250 GeV, with a well defined upgrade path to 550 GeV while staying on the same short facility footprint [2,3]. C 3 is based on a fundamentally new approach to normal conducting linear accelerators that achieves both high gradient and high efficiency at relatively low cost. Given the advanced state of linear collider designs, the key system that requires technical maturation for C 3 is the main linac. This paper presents the staged approach towards a facility to demonstrate C 3 technology with both Direct (source and main linac) and Parallel (beam delivery, damping ring, ancillary component) R&amp;D. The primary goal of the C 3 Demonstration R&amp;D Plan is to reduce technical and cost risk by building and operating the key components of C 3 at an adequate scale. This R&amp;D plan starts with the engineering design, and demonstration of one cryomodule and will culminate in the construction of a 3 cryomodule linac with pre-production prototypes. This R&amp;D program would also demonstrate the linac rf fundamentals including achievable gradient and gradient stability over a full electron bunch train and breakdown rates. It will also investigate beam dynamics including energy spread, wakefields, and emittance growth. This work will be critical to confirm the suitability of the C 3 beam parameters for the physics reach and detector performance in preparation for a Conceptual Design Report (CDR), as well as for follow-on technology development and industrialization. The C 3 Demonstration R&amp;D Plan will open up significant new scientific and technical opportunities based on development of high-gradient and high-efficiency accelerator technology. It will push this technology to operate both at the GeV scale and mature the technology to be reliable and provide high-brightness electron beams. The timeline for progressing with C 3 technology development will be governed by practical limitations on both the technical progress and resource availability. It consists of four stages: Stage 0) Ongoing fundamental R&amp;D on structure prototypes, damping and vibrations. Stage 1) Advancing the engineering maturity of the design and developing start-to-end simulations including space-charge and wakefield effects. This stage will include testing of strucutres operating at cryogenic temperatures. Beam tests would be performed with high beam current to test full beam loading. Stage 2) Production and testing of the first cryomodule at cryogenic temperatures. This would provide sufficient experimental data to compile a CDR and it is anticipated for Stage 2 to last 3 years and to culminate with the transport of photo-electrons through the first cryomodule. Stage 3) Updates to the engineering design of the cryomodules, production of the second and third cryomodule and their installation. Lower charge and lower emittance beams will be used to investigate emittance growth. The successful full demonstration of the 3 cryomodules to deliver up to a 3 GeV beam and achieve the C 3 five gradient will allow a comprehensive and robust evaluation of the technical design of C 3 as well as mitigate technical, schedule, and cost risks required to proceed with a Technical Design Report (TDR).