Observation of Orbitally Excited B_s Mesons

We report the first observation of two narrow resonances consistent with states of orbitally excited (L=1) B_s mesons using 1 fb^{-1} of ppbar collisions at sqrt{s} = 1.96 TeV collected with the CDF II detector at the Fermilab Tevatron. We use two-body decays into K^- and B^+ mesons reconstructed as B^+ \to J/\psi K^+, J/\psi \to \mu^+ \mu^- or B^+ \to \bar{D}^0 \pi^+, \bar{D}^0 \to K^+ \pi^-. We deduce the masses of the two states to be m(B_{s1}) = 5829.4 +- 0.7 MeV/c^2 and m(B_{s2}^*) = 5839.7 +- 0.7 MeV/c^2.Comment: Version accepted and published by Phys. Rev. Let

Search for Maximal Flavor Violating Scalars in Same-Charge Lepton Pairs in pp̅ Collisions at √s=1.96 TeV

Models of Maximal Flavor Violation (MxFV) in elementary particle physics may contain at least one new scalar SU$(2)$ doublet field $\Phi_{FV} = (\eta^0,\eta^+)$ that couples the first and third generation quarks ($q_1,q_3$) via a Lagrangian term $\mathcal{L}_{FV} = \xi_{13} \Phi_{FV} q_1 q_3$. These models have a distinctive signature of same-charge top-quark pairs and evade flavor-changing limits from meson mixing measurements. Data corresponding to 2 fb$^{-1}$ collected by the CDF II detector in $p\bar{p}$ collisions at $\sqrt{s} = 1.96$ TeV are analyzed for evidence of the MxFV signature. For a neutral scalar $\eta^0$ with $m_{\eta^0} = 200$ GeV/$c^2$ and coupling $\xi_{13}=1$, $\sim$ 11 signal events are expected over a background of $2.1 \pm 1.8$ events. Three events are observed in the data, consistent with background expectations, and limits are set on the coupling $\xi_{13}$ for $m_{\eta^0} = 180-300$ GeV/$c^2$.Models of maximal flavor violation (MxFV) in elementary particle physics may contain at least one new scalar SU(2) doublet field ΦFV=(η0,η+) that couples the first and third generation quarks (q1, q3) via a Lagrangian term LFV=ξ13ΦFVq1q3. These models have a distinctive signature of same-charge top-quark pairs and evade flavor-changing limits from meson mixing measurements. Data corresponding to 2  fb-1 collected by the Collider Dectector at Fermilab II detector in pp̅ collisions at √s=1.96  TeV are analyzed for evidence of the MxFV signature. For a neutral scalar η0 with mη0=200  GeV/c2 and coupling ξ13=1, ~11 signal events are expected over a background of 2.1±1.8 events. Three events are observed in the data, consistent with background expectations, and limits are set on the coupling ξ13 for mη0=180–300  GeV/c2.Peer reviewe

Measurement of inclusive jet cross sections in Z/gamma*(-\u3e e(+)e(-))+jets production in p(p)over-bar collisions at root s=1.96 TeV

Inclusive jet cross sections in Z/gamma* events, with Z/gamma* decaying into an electron-positron pair, are measured as a function of jet transverse momentum and jet multiplicity in p (p) over bar collisions at root s=1.96 TeV with the upgraded Collider Detector at Fermilab in run II, based on an integrated luminosity of 1.7 fb(-1). The measurements cover the rapidity region |y(jet)|\u3c2.1 and the transverse momentum range p(T)(jet)\u3e30 GeV/c. Next-to-leading order perturbative QCD predictions are in good agreement with the measured cross sections

Measurement of the cross section for W-boson production in association with jets in ppbar collisions at sqrt(s)=1.96 TeV

We present a measurement of the cross section for W-boson production in association with jets in pbar-p collisions at sqrt(s)=1.96 TeV. The analysis uses a data sample corresponding to an integrated luminosity of 320 pb^-1 collected with the CDF II detector. W bosons are identified in their electron decay channel and jets are reconstructed using a cone algorithm. For each W+>= n-jet sample (n= 1 - 4) we measure dsigma(ppbar =>W+>=n-jet)/dE_T^(nth-jet) x BR(W => e nu) with respect to the transverse energy E_T of the n^th-highest E_T jet above 20 GeV, and the total cross section sigma(ppbar =>W+>=n-jet; E_T^(nth-jet)>25 GeV) x BR(W => e nu), for a restricted W => e nu decay phase space. The cross sections, corrected for all detector effects, can be directly compared to particle level W+ jet(s) predictions. We present here comparisons to leading order and next-to-leading order predictions.Comment: Submitted to Phys. Rev. D rapid communicatio

First Measurement of the Fraction of Top Quark Pair Production Through Gluon-Gluon Fusion

We present the first measurement of the fraction of top quark pair production through gluon-gluon fusion. We use 0.96/fb of s**(1/2)=1.96 TeV p-pbar collision data recorded with the CDF II detector at Fermilab. We identify the candidate t-tbar events with a high-energy charged lepton, a neutrino candidate, and four or more jets. Using charged particles with low transverse momentum in t-tbar events, we find the fraction of top quark pair production through gluon-gluon fusion to be 0.07+/-0.14(stat)+/-0.07(syst), corresponding to a 95% confidence level upper limit of 0.33, in agreement with the standard model NLO prediction of 0.15+/-0.05.Comment: 6 pages, 2 figures, Submitted to Phys.Rev.Lett, added 95% CL upper limi

Evidence for D0-D0bar mixing using the CDF II Detector

We measure the time dependence of the ratio of decay rates for the rare decay D0->K+pi- to the Cabibbo-favored decay D0->K-pi+. We use a signal of 12.7 x10^3 D0->K+pi decays with proper decay times between 0.75 and 10 mean D0 lifetimes. The data sample was recorded with the CDF II detector at the Fermilab Tevatron and corresponds to an integrated luminosity of 1.5 fb-1 of p-pbar collisions at sqrt(s) = 1.96 TeV. We search for D0-D0bar mixing and measure the mixing parameters to be Rd = (3.04 +/- 0.55) x10^{-3}, y' = (8.5 +/- 7.6) x10^{-3}, and x'^2 = (-0.12 +/- 0.35) x10^{-3}. We report Bayesian probability contours in the x'^2-y' plane and find that the data are inconsistent with the no-mixing hypothesis with a probability equivalent to 3.8 Gaussian standard deviations.Comment: 7 pages, 4 figures, submitted to Phys. Rev. Let

Search for chargino-neutralino production in p(p)over-bar collisions at root s=1.96 TeV with high-p(T) leptons

We present a search for the associated production of charginos and neutralinos in p (p) over bar collisions at root s = 1.96 TeV. The data were collected at the Collider Detector at Fermilab (CDF II) and correspond to integrated luminosities between 0.7 and 1.0 fb(-1). We look for final states with one high-p(T) electron or muon, and two additional leptons. Our results are consistent with the standard model expectations, and we set limits on the cross section as a function of the chargino mass in three different supersymmetric scenarios. For a specific minimal supersymmetric standard model scenario with no slepton mixing, we set a 95% C. L. limit at 151 GeV/c(2)

Limits on the Production of Narrow t-tbar Resonances in p-pbar Collisions at sqrt(s)=1.96 TeV

We search for evidence of resonant top quark pair production in 955 pb-1 of p-pbar collisions at sqrt(s)=1.96 TeV recorded with the CDF II detector at the Fermilab Tevatron. For fully reconstructed candidate t-tbar events triggered on leptons with large transverse momentum and containing at least one identified b-quark jet, we compare the invariant mass spectrum of t-tbar pairs to the expected superposition of standard model t-tbar, non-t-tbar backgrounds, and a simple resonance model based on a sequential Z' boson. We establish upper limits for sigma(p-pbar to Z') times Br(Z' to t-tbar) in the Z' mass interval from 450 GeV/c2 to 900 GeV/c2. A topcolor leptophobic Z' is ruled out below 720 GeV/c2, and the cross section of any narrow Z'-like state decaying to t-tbar is found to be less than 0.64 pb at 95% C.L. for M(Z') above 700 GeV/c2.Comment: 7 Pages, 3 eps Figures; when using dvips use "-t letter -P pdf" option; To be submitted to Phys. Rev. D Rapid Communication

Copper‐Based Corrole as Thermally Stable Hole Transporting Material for Perovskite Photovoltaics

Perovskite solar cells (PSCs) represent nowadays a promising starting point to develop a new efficient and low-cost photovoltaic technology due to the demonstrated power conversion efficiency (PCE) exceeding 25% on small area devices. However, best reported devices suffer from stability issue under real working conditions thus slowing down the race for the commercialization. In particular, the hole transporting material commonly employed in mesoscopic n–i–p PSCs (nip-mPSCs), namely spiro-OMeTAD, is strongly corrupted when subjected to temperatures above 70 °C due to intrinsic thermal instability and because of the dopant employed to improve the hole mobility. In this work, the novel use of a copper-based corrole as HTM is proposed to improve the device thermal stability of nip-mPSCs under prolonged 85 °C stress conditions. Corrole-based devices show remarkable PCE above 16% by retaining more than 65% of the initial PCE after 1000 h of thermal stress, while spiro-OMeTAD cells abruptly lose more than 60% after the first 40 h. Once scaled-up to large area modules, the proposed device structure can truly represent a possible way to pass thermal stress tests proposed by IEC-61646 standards and, not less importantly, the high temperature required by the lamination process for panel production

First observation of the decay B-s(0)-\u3e Ds-Ds+ and measurement of its branching ratio

We report the observation of the exclusive decay B-s(0)-\u3e Ds-Ds+ at the 7.5 standard deviation level using 355 pb(-1) of data collected by the CDF II detector in p (p) over bar collisions at root s =1.96 TeV at the Fermilab Tevatron. We measure the relative branching ratio B(B-s(0)-\u3e Ds-Ds+)/B(B-0 -\u3e D-Ds+)=1.44(-0.44)(+0.48). Using the world average value for B(B-0 -\u3e D-Ds+), we find B(B-s(0)-\u3e Ds-Ds+)=(9.4(-4.2)(+4.4))x10(-3). This provides a lower bound Delta Gamma(CP)(s)/Gamma(s)\u3e= 2B(B-s(0)-\u3e Ds-Ds+)\u3e 1.2x10(-2) at 95% C.L