Limits on anomalous trilinear gauge couplings in Zγ events from pp¯ collisions at √s=1.96 TeV

Using Zγ candidate events collected by the CDF detector at the Tevatron Collider, we search for potential anomalous (non-standard-model) couplings between the Z boson and the photon. Zγ couplings vanish at tree level and are heavily suppressed at higher orders; hence any evidence of couplings indicates new physics. Measurements are performed using data corresponding to an integrated luminosity of 4.9  fb(-1) in the Z→νν¯ decay channel and 5.1  fb(-1) in the Z→l(+)l(-) (l=μ, e) decay channels. The combination of these measurements provides the most stringent limits to date on Zγ trilinear gauge couplings. Using an energy scale of Λ=1.5  TeV to allow for a direct comparison with previous measurements, we find limits on the CP-conserving parameters that describe Zγ couplings to be |h(3)(γ,Z)|<0.022 and |h(4)(γ,Z)|<0.0009. These results are consistent with standard model predictions.

First search for multijet resonances in sqrt(s) = 1.96 TeV pp collisions

We present the first model independent search for three-jet hadronic resonances within multijet events in sqrt(s) = 1.96  TeV pp collisions at the Fermilab Tevatron using the CDF II detector. Pair production of supersymmetric gluinos and squarks with hadronic R-parity violating decays is employed as an example of a new physics benchmark for this signature. Selection criteria based on the kinematic properties of an ensemble of jet combinations within each event help to extract signal from copious QCD background. No significant excess outside the top quark mass window is observed in data with an integrated luminosity of 3.2  fb(-1). We place 95% confidence level limits on the production cross section σ(pp → XX')×BR(gg → 3  jet + 3  jet) where X, X' = g, q, or q, with q, q → g + jet, as a function of gluino mass, in the range of 77  GeV/c2 to 240  GeV/c2.

Search for a very light CP-odd Higgs boson in top quark decays from pp collisions at sqrt(s)]=1.96 TeV

We present the results of a search for a very light CP-odd Higgs boson a(1)(0) originating from top quark decays t → H(±)b → W(±(*)) a(1)(0)b, and subsequently decaying into τ+ τ-. Using a data sample corresponding to an integrated luminosity of 2.7  fb(-1) collected by the CDF II detector in pp collisions at 1.96 TeV, we perform a search for events containing a lepton, three or more jets, and an additional isolated track with transverse momentum in the range 3 to 20  GeV/c. Observed events are consistent with background sources, and 95% C.L. limits are set on the branching ratio of t → H(±)b for various masses of H(±) and a(1)(0).

Fabrication and manipulation of solid-state SiO2 nano-gears on a gold surface

A process is presented to fabricate solid-state nano-gears down to a 60 nm outer diameter with six teeth, where the 350 nm diameter ones already have 24 teeth. The small gears are free to move on a polycrystalline gold surface. The gears can be manipulated one by one, using an atomic force microscope (AFM) tip, to construct a train of gears where mechanical motion can be transmitted from one gear to another by mastering the surface friction. This is a first step on the way to bridge the fabrication gap between microfabricated and molecule gears.

First measurement of the angular coefficients of Drell-Yan e(+)e(-) pairs in the Z mass region from pp¯ collisions at √s=1.96 TeV

We report on the first measurement of the angular distributions of final state electrons in pp¯ → γ*/Z → e(+)e(-) + X events produced in the Z boson mass region at √s1.96 TeV. The data sample collected by the CDF II detector for this result corresponds to 2.1  fb(-1) of integrated luminosity. The angular distributions are studied as a function of the transverse momentum of the electron-positron pair and show good agreement with the Lam-Tung relation, consistent with a spin-1 description of the gluon, and demonstrate that, at high values of the transverse momentum, Z bosons are produced via quark-antiquark annihilation and quark-gluon Compton processes.

Search for production of heavy particles decaying to top quarks and invisible particles in pp collisions at √s = 1.96 TeV

We present a search for a new particle T' decaying to top quark via T' → t + X, where X is an invisible particle. In a data sample with 4.8  fb(-1) of integrated luminosity collected by the CDF II detector at Fermilab in pp collisions with √s = 1.96  TeV, we search for pair production of T' in the lepton + jets channel, pp → tt + X + X → ℓνbqq'b + X + X. We interpret our results primarily in terms of a model where T' are exotic fourth generation quarks and X are dark matter particles. Current direct and indirect bounds on such exotic quarks restrict their masses to be between 300 and 600  GeV/c2, the dark matter particle mass being anywhere below m(T'). The data are consistent with standard model expectations, and we set 95% confidence level limits on the generic production of T'T' → tt + X + X. For the dark matter model we exclude T' at 95% confidence level up to m(T') = 360  GeV/c2 for m(X) ≤ 100  GeV/c2.

Measurements of direct CP violating asymmetries in charmless decays of strange bottom mesons and bottom baryons

We report measurements of direct CP-violating asymmetries in charmless decays of neutral bottom hadrons to pairs of charged hadrons with the upgraded Collider Detector at the Fermilab Tevatron. Using a data sample corresponding to 1 fb(-1) of integrated luminosity, we obtain the first measurements of direct CP violation in bottom strange mesons, A(CP)(B(s)(0)→K(-)π(+))=+0.39±0.15(stat)±0.08(syst), and bottom baryons, A(CP)(Λ(b)(0)→pπ(-))=+0.03±0.17(stat)±0.05(syst) and A(CP)(Λ(b)(0)→pK(-))=+0.37±0.17(stat)±0.03(syst). In addition, we measure CP violation in B(0)→K(+)π(-) decays with 3.5σ significance, A(CP)(B(0)→K(+)π(-))=-0.086±0.023(stat)±0.009(syst), in agreement with the current world average. Measurements of branching fractions of B(s)(0)→K(+)K(-) and B(0)→π(+)π(-) decays are also updated.

Invariant mass distribution of jet pairs produced in association with a W boson in pp collisions at sqrt[s]=1.96 TeV

We report a study of the invariant mass distribution of jet pairs produced in association with a W boson using data collected with the CDF detector which correspond to an integrated luminosity of 4.3  fb(-1). The observed distribution has an excess in the 120-160  GeV/c(2) mass range which is not described by current theoretical predictions within the statistical and systematic uncertainties. In this Letter, we report studies of the properties of this excess.

Measurement of the forward-backward asymmetry in the B→K*μ(+)μ(-) decay and first observation of the B(s)0→ϕμ(+)μ(-) decay

We reconstruct the rare decays B(+)→K(+)μ(+0μ(-0, B90)→K*(892)(0)μ(+)μ(-), and B(s)(0)→ϕ(1020)μ(+)μ(-) in a data sample corresponding to 4.4  fb(-1) collected in pp collisions at √[s]=1.96  TeV by the CDF II detector at the Tevatron Collider. Using 121±16 B(+)→K(+)μ(+)μ(-) and 101±12 B(0)→K(*0)μ(+)μ(-) decays we report the branching ratios. In addition, we report the differential branching ratio and the muon forward-backward asymmetry in the B(+) and B(0) decay modes, and the K(*0) longitudinal polarization fraction in the B(0) decay mode with respect to the squared dimuon mass. These are consistent with the predictions, and most recent determinations from other experiments and of comparable accuracy. We also report the first observation of the B(s)(0)→ϕμ(+)μ(-) decay and measure its branching ratio BR(B(s)(0)→ϕμ(+)μ(-))=[1.44±0.33±0.46]×10(-6) using 27±6 signal events. This is currently the most rare B(s)(0) decay observed.

Measurement of the mass difference between t and t quarks

We present a direct measurement of the mass difference between t and t quarks using tt candidate events in the lepton+jets channel, collected with the CDF II detector at Fermilab's 1.96 TeV Tevatron pp Collider. We make an event by event estimate of the mass difference to construct templates for top quark pair signal events and background events. The resulting mass difference distribution of data is compared to templates of signals and background using a maximum likelihood fit. From a sample corresponding to an integrated luminosity of 5.6  fb(-1), we measure a mass difference, ΔM(top) = M(t) - M(t) = -3.3 ± 1.4(stat) ± 1.0(syst)  GeV/c2, approximately 2 standard deviations away from the CPT hypothesis of zero mass difference.

Search for heavy bottomlike quarks decaying to an electron or muon and jets in pp collisions at √s = 1.96 TeV

We report the most sensitive direct search for pair production of fourth-generation bottomlike chiral quarks (b') each decaying promptly to tW. We search for an excess of events with an electron or muon, at least five jets (one identified as due to a b or c quark), and an imbalance of transverse momentum by using data from pp collisions collected by the CDF II detector at Fermilab with an integrated luminosity of 4.8  fb(-1). We observe events consistent with background expectation, calculate upper limits on the b' pair-production cross section (σ(bb')) ≲30  fb for m(b') > 375  GeV/c2), and exclude m(b') < 372  GeV/c2 at 95% confidence level assuming a 100% branching ratio of b' to tW.

Measurement of b hadron lifetimes in exclusive decays containing a J/ψ in pp collisions at √s=1.96 TeV

We report on a measurement of b-hadron lifetimes in the fully reconstructed decay modes B(+)→J/ψK(+), B⁰→J/ψK*(892)⁰, B⁰→J/ψK(s)⁰, and Λ(b)⁰→J/ψΛ⁰ using data corresponding to an integrated luminosity of 4.3 fb⁻¹, collected by the CDF II detector at the Fermilab Tevatron. The measured lifetimes are τ(B(+))=[1.639±0.009(stat)±0.009(syst)] ps, τ(B⁰)=[1.507±0.010(stat)±0.008(syst)] ps, and τ(Λ(b)⁰)=[1.537±0.045(stat)±0.014(syst)] ps. The lifetime ratios are τ(B(+))/τ(B⁰)=[1.088±0.009(stat)±0.004(syst)] and τ(Λ(b)⁰)/τ(B⁰)=[1.020±0.030(stat)±0.008(syst)]. These are the most precise determinations of these quantities from a single experiment.

Search for high mass resonances decaying to muon pairs in √s=1.96 TeV pp collisions

We present a search for a new narrow, spin-1, high mass resonance decaying to μ(+)μ⁻+X, using a matrix-element-based likelihood and a simultaneous measurement of the resonance mass and production rate. In data with 4.6 fb⁻¹ of integrated luminosity collected by the CDF detector in pp collisions at √s=1960 GeV, the most likely signal cross section is consistent with zero at 16% confidence level. We therefore do not observe evidence for a high mass resonance and place limits on models predicting spin-1 resonances, including M>1071 GeV/c² at 95% confidence level for a Z' boson with the same couplings to fermions as the Z boson.

Serological and virological surveillance of swine H1N1 and H3N2 influenza virus infection in two farms located in Hubei province, central China

Swine influenza viruses H1N1 and H3N2 have been reported in the swine population worldwide. From June 2008 to June 2009, we carried out serological and virological surveillance of swine influenza in the Hubei province in central China. The serological results indicated that antibodies to H1N1 swine influenza virus in the swine population were high with a 42.5% (204/480) positive rate, whereas antibodies to H3N2 swine influenza virus were low with a 7.9% (38/480) positive rate. Virological surveillance showed that only one sample from weanling pigs was positive by RT-PCR. Phylogenetic analysis of the hemagglutinin and neuraminidase genes revealed that the A/Sw/HB/S1/2009 isolate was closely related to avian-like H1N1 viruses and seemed to be derived from the European swine H1N1 viruses. In conclusion, H1N1 influenza viruses were more dominant in the pig population than H3N2 influenza viruses in central China, and infection with avian-like H1N1 viruses persistently emerged in the swine population in the area.

Genetic diversity and differentiation in Dalbergia sissoo (Fabaceae) as revealed by RAPD

Dalbergia sissoo, a wind-dispersed tropical tree, is one of the most preferred timber tree species of South Asia. Genetic diversity and differentiation among natural populations of D. sissoo were examined for the first time. We found a relatively high level of genetic diversity in D. sissoo, both at the species level (percentage of polymorphic bands = 89.11%; H = 0.2730; I = 0.4180) and the population level (percentage of polymorphic bands = 68.7%; H = 0.239; I = 0.358), along with a relatively low degree of differentiation among populations (GST = 0.1311; AMOVA = 14.69%). Strong gene flow among populations was estimated, N(m) = 3.3125. The Mantel test suggested that genetic distances between populations were weakly correlated with geographic distances (R = 0.3702, P = 0.1236). The high level of genetic diversity, low degree of differentiation, strong gene flow, and weak correlation between genetic and geographic distances can be explained by its biological character and wide-spread planting. This information will be useful for the introduction, conservation and further studies of D. sissoo and related species.

Investigation of optimal aminolaevulinic acid concentration applied in topical aminolaevulinic acid-photodynamic therapy for treatment of moderate to severe acne: a pilot study in Chinese subjects

BACKGROUND

Aminolaevulinic acid-photodynamic therapy (ALA-PDT) is a novel and effective treatment in acne. However, little is known about the effect of different concentrations of ALA in the treatment of acne in Chinese patients with Fitzpatrick skin type III and IV.

OBJECTIVES

To investigate the efficacy and safety of ALA-PDT in the treatment of moderate to severe acne in Chinese patients and to identify the suitable concentration of topical ALA.

METHODS

One hundred and eighty patients with moderate to severe facial acne were recruited and randomly divided into four groups. Each group was treated with a different concentration (5%, 10%, 15% and 20%) of ALA to the facial lesions on the right side and placebo agent on the left side as control. Each patient was treated once every 10 days for four sessions. The numbers of inflammatory and noninflammatory acne lesions were counted at baseline and at weeks 2, 4, 12 and 24 after the last treatment. Adverse effects were recorded at each follow-up visit.

RESULTS

After 24 weeks, each side treated by ALA-PDT showed clinical improvement compared with the control side treated by red light alone (P < 0·01). Statistically significantly more patients treated with 20% ALA than with 15% or 10% ALA achieved complete clearance. Regarding side-effects, a trend towards more serious erythema and pigmentation was observed with increasing ALA concentration.

CONCLUSIONS

Increasing the concentration of ALA seems to be beneficial for improving the results. Considering effectiveness and safety, ALA-PDT using 10% or 15% ALA is suggested to the ideal treatment for moderate to severe acne in Chinese patients with Fitzpatrick skin type III and IV.

Top quark mass measurement in the lepton + jets channel using a matrix element method and in situ jet energy calibration

A precision measurement of the top quark mass m(t) is obtained using a sample of tt events from pp collisions at the Fermilab Tevatron with the CDF II detector. Selected events require an electron or muon, large missing transverse energy, and exactly four high-energy jets, at least one of which is tagged as coming from a b quark. A likelihood is calculated using a matrix element method with quasi-Monte Carlo integration taking into account finite detector resolution and jet mass effects. The event likelihood is a function of m(t) and a parameter Δ(JES) used to calibrate the jet energy scale in situ. Using a total of 1087 events in 5.6 fb(-1) of integrated luminosity, a value of m(t)=173.0 ± 1.2 GeV/c(2) is measured.

Improved search for a Higgs boson produced in association with Z → l+ l- in pp collisions sqrt[s] = 1.96 TeV

We search for the standard model Higgs boson produced with a Z boson in 4.1 fb(-1) of integrated luminosity collected with the CDF II detector at the Tevatron. In events consistent with the decay of the Higgs boson to a bottom-quark pair and the Z boson to electrons or muons, we set 95% credibility level upper limits on the ZH production cross section multiplied by the H → bb branching ratio. Improved analysis methods enhance signal sensitivity by 20% relative to previous searches. At a Higgs boson mass of 115 GeV/c2 we set a limit of 5.9 times the standard model cross section.