arXiv subjects

D. Acosta

Publications and source records attributed to D. Acosta.

At least 37 records · Page 2Linked to original sources

arXiv2005

Search for Lambda_b -> p pi and Lambda_b -> p K decays in p-pbar collisions at sqrt(s) = 1.96 TeV

We report on a search for Lambda_b -> p pi- and Lambda_b -> p K- (and charge conjugate) decays in p-pbar collisions at sqrt(s) = 1.96 TeV using 193 pb-1 of data collected by CDFII experiment at the Fermilab Tevatron Collider. Data were collected using a track trigger that has been optimized to select tracks belonging to a secondary vertex that is typical of two body charmless decays of b-flavored hadrons, including Lambda_b baryons. As no Lambda_b signal was observed, we set the upper limits on the branching fractions BR(Lambda_b -> p h-) where h is K or pi, of 2.3x10-5 at 90% C.L. and 2.9x10-5 at 95% C.L.

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arXiv2005

Search for Anomalous Kinematics in ttbar Dilepton Events at CDF II

We report on a search for anomalous kinematics of ttbar dilepton events in ppbar collisions at sqrt{s}=1.96 TeV using 193 {pb}^{-1} of data collected with the CDF II detector. We developed a new a priori technique designed to isolate the subset in a data sample revealing the largest deviation from standard model (SM) expectations and to quantify the significance of this departure. In the four-variable space considered, no particular subset shows a significant discrepancy and we find that the probability of obtaining a data sample less consistent with the SM than what is observed is 1.0-4.5%.

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arXiv2005

Search for W and Z Bosons in the Reaction \bar{p}p \to 2 jets + γat \sqrt{s} = 1.8 TeV

We present a study of the dijet invariant mass distribution for the reaction $\pbp \to 2 $jets$+γ+X$, at a center of mass energy of 1.8 TeV, using data collected by the CDF experiment. We compare the data to predictions for the production of a photon with two jets, together with the resonant processes $\pbp \to W/Z+γ+X$, in which the $W$ and $Z$ bosons decay hadronically. A fit is made to the dijet invariant mass distribution combining the non-resonant background and resonant processes. We use the result to establish a limit for the inclusive production cross section of $W/Z+γ$ with hadronic decay of the $W$ and $Z$ bosons.

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arXiv2005

Search for First-Generation Scalar Leptoquarks in $\bm{p \bar{p}}$ collisions at $\sqrt{s}$=1.96 TeV

We report on a search for pair production of first-generation scalar leptoquarks ($LQ$) in $p \bar{p}$ collisions at $\sqrt{s}$=1.96 TeV using an integrated luminosity of 203 $pb^{-1}$ collected at the Fermilab Tevatron collider by the CDF experiment. We observe no evidence for $LQ$ production in the topologies arising from $LQ \bar{LQ} \to eqeq$ and $LQ \bar{LQ} \to eq νq$, and derive 95% C.L. upper limits on the $LQ$ production cross section. %as a function of $β$, where $β$ is the branching fraction for $LQ \to eq$. The results are combined with those obtained from a separately reported CDF search in the topology arising from $LQ\bar{LQ} \to νq νq$ and 95% C.L. lower limits on the LQ mass as a function of $β= BR(LQ \to eq) $ are derived. The limits are 236, 205 and 145 GeV/c$^2$ for $β$ = 1, $β$ = 0.5 and $β$ = 0.1, respectively.

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arXiv2005

A Search for Supersymmetric Higgs Bosons in the Di-Tau Decay Mode in Proton Anti-Proton Collisions at sqrt(s)=1.8 TeV

A search for direct production of Higgs bosons in the di-tau decay mode is performed with 86.3 +/- 3.5 pb^-1 of data collected with the Collider Detector at Fermilab during the 1994-1995 data taking period of the Tevatron. We search for events where one tau decays to an electron plus neutrinos and the other tau decays hadronically. We perform a counting experiment and set limits on the cross section for supersymmetric Higgs boson production where tan(beta) is large and m_A is small. For a benchmark parameter space point where m_A=100 GeV/c^2 and tan(beta)=50, we limit the production cross section multiplied by the branching ratio to be less than 77.9 pb at the 95% confidence level compared to the theoretically predicted value of 11.0 pb. This is the first search for Higgs bosons decaying to tau pairs at a hadron collider.

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arXiv2005

First Evidence for $B_s^0 \to ϕϕ$ Decay and Measurements of Branching Ratio and $A_{CP}$ for $B^+ \to ϕK^+$

We present the first evidence of charmless decays of the $B_s^0$ meson, the decay \phiphi, and a measurement of the Branching Ratio $\BR(\phiphi)$ using $180 {\rm pb}^{-1}$ of data collected by the \cdfii experiment at the Fermilab Tevatron collider. In addition, the BR and direct CP asymmetry for the \phik\ decay are measured. We obtain: $\BR (\phiphi) = (14 \ase{6}{5}(stat.) \pm 6(syst.)) \times 10^{-6}$, $\BR (\phik) = (7.6 \pm 1.3(stat.) \pm 0.6(syst.)) \times 10^{-6}$, and $\ACP(\phik) = -0.07 \pm 0.17 (stat.) \ase{0.03}{0.02} (syst.)$. Both decays are governed in the Standard Model by second order (penguin) $b \myto s\bar{s}s$ amplitudes.

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arXiv2005

The Discovery Potential of Supersymmetry at CMS within the mSUGRA Model Using Same-Sign Di-Muons

A detailed study of the same-sign muon signature within the mSUGRA model is described. Selection criteria based on the missing transverse energy in the events and the jet and muon transverse momenta are applied. The results indicate that an excess of SUSY events over the Standard Model background processes can be statistically significant for an integrated luminosity of less than 10 fb^-1 for many benchmark points with m_1/2 up to 650 GeV/c^2.

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arXiv2005

Measurement of the Lifetime Difference Between B_s Mass Eigenstates

We present measurements of the lifetimes and polarization amplitudes for B_s --> J/psi phi and B_d --> J/psi K*0 decays. Lifetimes of the heavy (H) and light (L) mass eigenstates in the B_s system are separately measured for the first time by determining the relative contributions of amplitudes with definite CP as a function of the decay time. Using 203 +/- 15 B_s decays, we obtain tau_L = (1.05 +{0.16}/-{0.13} +/- 0.02) ps and tau_H = (2.07 +{0.58}/-{0.46} +/- 0.03) ps. Expressed in terms of the difference DeltaGamma_s and average Gamma_s, of the decay rates of the two eigenstates, the results are DeltaGamma_s/Gamma_s = (65 +{25}/-{33} +/- 1)%, and DeltaGamma_s = (0.47 +{0.19}/-{0.24} +/- 0.01) inverse ps.

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arXiv2005

K_s^0 and Lambda^0 Production Studies in pbar-p Collisions at sqrt(s)=1800 and 630 GeV

We present a study of the production of K_s^0 and Lambda^0 in inelastic pbar-p collisions at sqrt(s)= 1800 and 630 GeV using data collected by the CDF experiment at the Fermilab Tevatron. Analyses of K_s^0 and Lambda^0 multiplicity and transverse momentum distributions, as well as of the dependencies of the average number and of K_s^0 and Lambda^0 on charged particle multiplicity are reported. Systematic comparisons are performed for the full sample of inelastic collisions, and for the low and high momentum transfer subsamples, at the two energies. The p_T distributions extend above 8 GeV/c, showing a higher than previous measurements. The dependence of the mean K_s^0(Lambda^0) p_T on the charged particle multiplicity for the three samples shows a behavior analogous to that of charged primary tracks.

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arXiv2005

Measurement of the Forward-Backward Charge Asymmetry from W --> e nu Production in p anti-p Collisions at s**(1/2) = 1.96 TeV

We report a measurement of the forward-backward charge asymmetry of electrons from W boson decays in p anti-p collisions at s**(1/2) = 1.96 TeV using a data sample of 170 pb-1 collected by the Collider Detector at Fermilab. The asymmetry is measured as a function of electron rapidity and transverse energy and provides new input on the momentum fraction dependence of the u and d quark parton distribution within the proton.

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arXiv2005

Measurement of the azimuthal angle distribution of leptons from W boson decays as a function of the W transverse momentum in proton-antiproton collisions at sqrt(s)=1.8 TeV

We present the first measurement of the A_2 and A_3 angular coefficients of the W boson produced in proton-antiproton collisions. We study W-> e+nu and W-> mu+nu candidate events produced in association with at least one jet at CDF, during Run Ia and Run Ib of the Tevatron at sqrt(s)=1.8 TeV. The corresponding integrated luminosity was 110 pb^-1. The jet balances the transverse momentum of the W and introduces QCD effects in W boson production. The extraction of the angular coefficients is achieved through the direct measurement of the azimuthal angle of the charged lepton in the Collins-Soper rest-frame of the W boson. The angular coefficients are measured as a function of the transverse momentum of the W boson. The electron, muon, and combined results are in good agreement with the Standard Model prediction, up to order alpha_s^2 in QCD.

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arXiv2005

Measurement of the Moments of the Hadronic Invariant Mass Distribution in Semileptonic B Decays

Using 180 pb^-1 of data collected with the CDF II detector at the Tevatron, we measure the first two moments of the hadronic invariant mass-squared distribution in charmed semileptonic B decays. From these we determine the non-perturbative Heavy Quark Effective Theory parameters Lambda and lambda_1, used to relate the B meson semileptonic branching ratio to the CKM matrix element |V_cb|. For a minimum lepton momentum of 0.7 GeV/c in the B rest frame me measure the first two moments of the D** --> D(*) pi component to be = (5.83 +/- 0.16(stat) +/- 0.08(syst)) GeV^2, <(m^2_D** - )^2> = (1.30 +/- 0.69(stat) +/- 0.22(syst)) GeV^4. Combining these with the discrete mass terms from the D and D* mesons, we find the total moments to be - mbar_D^2 = (0.467 +/- 0.038_(stat) +/- 0.068(syst)) GeV^2, <(M^2_Xc - )^2> = (1.05 +/- 0.26(stat) +/- 0.13(syst)) GeV^4, where mbar_D is the spin-averaged D mass. The systematic error is dominated by the uncertainties in the world-average branching ratios used to combine the D, D* and D** contributions. The analysis makes no assumptions about the shape or resonant structure of the D** --> D(*) pi invariant mass distribution.

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arXiv2005

Search for Long-Lived Doubly-Charged Higgs Bosons in p-pbar Collisions at sqrt{s} = 1.96 TeV

We present a search for long-lived doubly-charged Higgs bosons (H^{\pm \pm}), with signatures of high ionization energy loss and muon-like penetration. We use 292/pb of data collected in p-pbar collisions at sqrt{s} = 1.96 TeV by the CDF II detector at the Fermilab Tevatron. Observing no evidence of long-lived doubly-charged particle production, we exclude H^{\pm \pm}_L and H^{\pm \pm}_R bosons with masses below 133 GeV/c^2 and 109 GeV/c^2, respectively. In the degenerate case we exclude H^{\pm \pm} mass below 146 GeV/c^2. All limits are quoted at the 95% confidence level.

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arXiv2005

Search for Excited and Exotic Electrons in the e-gamma Decay Channel in p-pbar Collisions at sqrt(s) = 1.96 TeV

We present a search for excited and exotic electrons (e*) decaying to an electron and a photon, both with high transverse momentum. We use 202/pb of data collected in p-pbar collisions at sqrt(s) = 1.96 TeV with the CDF II detector. No signal above Standard Model expectation is seen for associated ee* production. We discuss the e* sensitivity in the parameter space of the excited electron mass M(e*) and the compositeness energy scale Lambda. In the contact interaction model, we exclude 132 < M(e*) < 879 GeV/c^2 for Lambda = M(e*) at 95% confidence level (C.L.). In the gauge-mediated model, we exclude 126 < M(e*) < 430 GeV/c^2 at 95% C.L. for the phenomenological coupling f/Lambda ~ 0.01/GeV.

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arXiv2005

Search for electroweak single top quark production in ppbar collisions at sqrt{s}=1.96 TeV

We report on a search for Standard Model t-channel and s-channel single top quark production in ppbar collisions at a center of mass energy of 1.96 TeV. We use a data sample corresponding to 162 pb^{-1} recorded by the upgraded Collider Detector at Fermilab. We find no significant evidence for electroweak top quark production and set upper limits at the 95% confidence level on the production cross section, consistent with the Standard Model: 10.1 pb for the t-channel, 13.6 pb for the s-channel and 17.8 pb for the combined cross section of t- and s-channel.

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arXiv2005

Measurement of the W+W- Production Cross Section in ppbar Collisions at sqrt(s)=1.96 TeV using Dilepton Events

We present a measurement of the W+W- production cross section using 184/pb of ppbar collisions at a center-of-mass energy of 1.96 TeV collected with the Collider Detector at Fermilab. Using the dilepton decay channel W+W- -> l+l-vvbar, where the charged leptons can be either electrons or muons, we find 17 candidate events compared to an expected background of 5.0+2.2-0.8 events. The resulting W+W- production cross section measurement of sigma(ppbar -> W+W-) = 14.6 +5.8 -5.1 (stat) +1.8 -3.0 (syst) +-0.9 (lum) pb agrees well with the Standard Model expectation.

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arXiv2004

Measurement of the J/Psi Meson and b-Hadron Production Cross Sections in ppbar Collisions at sqrt s = 1960 GeV

We present a new measurement of the inclusive and differential production cross sections of $J/ψ$ mesons and $b$-hadrons in proton-antiproton collisions at $\sqrt{s}=1960$ GeV. The data correspond to an integrated luminosity of 39.7 pb$^{-1}$ collected by the CDF Run II detector. We find the integrated cross section for inclusive $J/ψ$ production for all transverse momenta from 0 to 20 GeV/$c$ in the rapidity range $|y|<0.6$ to be $4.08 \pm 0.02 (stat)^{+0.36}_{-0.33} (syst) μ{\rm b}$. We separate the fraction of $J/ψ$ events from the decay of the long-lived $b$-hadrons using the lifetime distribution in all events with $p_T(J/ψ) > 1.25$ GeV/$c$. We find the total cross section for $b$-hadrons, including both hadrons and anti-hadrons, decaying to $J/ψ$ with transverse momenta greater than 1.25 GeV/$c$ in the rapidity range $|y(J/ψ)|<0.6$, is $ 0.330 \pm 0.005 (stat) ^{+0.036}_{-0.033} (syst) ~μ{\rm b}$. Using a Monte Carlo simulation of the decay kinematics of $b$-hadrons to all final states containing a $J/ψ$, we extract the first measurement of the total single $b$-hadron cross section down to zero transverse momentum at $\sqrt{s}=1960$ GeV. We find the total single $b$-hadron cross section integrated over all transverse momenta for $b$-hadrons in the rapidity range $|y|<0.6$ to be $ 17.6 \pm 0.4 (stat)^{+2.5}_{-2.3} (syst) μ{\rm b}$.

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arXiv2004

Search for Scalar Leptoquark Pairs Decaying to $ν\bar νq \bar q$ in \ppbar Collisions at $\sqrt {s} = 1.96$ TeV

We report on a search for the pair production of scalar leptoquarks, $LQ$, using 191 pb$^{-1}$ of proton-antiproton collision data recorded by the CDF experiment during Run II of the Tevatron. The leptoquarks are sought via their decay into a neutrino and quark yielding missing transverse energy and several jets of large transverse energy. No evidence for leptoquark production is observed, and limits are set on $σ(p\bar p\to LQ\bar{LQ} X \to ν\barνq\bar q X)$. Using a next-to-leading order theoretical prediction of the cross section for scalar leptoquark production, we exclude first-generation leptoquarks in the mass interval 78 to 117 GeV$/c^2$ at the 95% confidence level for BR($LQ\to νq)=100%$.

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