Search results for "Quark"
showing 10 items of 2905 documents
Top-quark mass measurements using jet rates at LHC
2013
This work presents a new method to measure the top-quark mass in hadronic collisions[1]. The method uses the sensitivity of the tt̄ + 1-jet production on the top-quark mass. In detail we study the ℛ distribution defined as the tt̄ + 1-jet normalized cross section differential in the invariant mass of the total system and calculated at NLO accuracy. We prove that the ℛ distribution has a high sensitivity to the top-quark mass. Furthermore we investigate and quantify the impact of the dominant theoretical and experimental uncertainties. The results obtained show, that the method has the potential to be competitive in precision with established approaches and allows a complementary measurement…
Measurement of the top quark mass using the invariant mass of lepton pairs in soft muon b-tagged events
2009
We present the first measurement of the mass of the top quark in a sample of t (t) over bar -> l (nu) over barb (b) over barq (q) over bar events (where l = e, mu) selected by identifying jets containing a muon candidate from the semileptonic decay of heavy-flavor hadrons (soft muon b tagging). The p (p) over bar collision data used correspond to an integrated luminosity of 2 fb(-1) and were collected by the CDF II detector at the Fermilab Tevatron Collider. The measurement is based on a novel technique exploiting the invariant mass of a subset of the decay particles, specifically the lepton from the W boson of the t -> Wb decay and the muon from a semileptonic b decay. We fit template hist…
Study of the semileptonic decays B→π, D→π and D→K
2006
The semileptonic decay B->pi is studied starting from a simple quark model that takes into account the effect of the B* resonance. A novel, multiply subtracted, Omnes dispersion relation has been implemented to extend the predictions of the quark model to all q^2 values accesible in the physical decay. By comparison to the experimental data, we extract |V_ub|=0.0034 +/- 0.0003(exp.) +/- 0.0007(theory). As a further test of the model, we have also studied D->pi and D->K decays for which we get good agreement with experiment.
Measurement of the Semileptonic Branching Ratio ofBs0to an Orbitally ExcitedDs**State:Br(Bs0→Ds1−(2536)μ+νX)
2009
In a data sample of approximately 1.3 fb-1 collected with the D0 detector between 2002 and 2006, the orbitally excited charm state D_s1(2536) has been observed with a measured mass of 2535.7 +/- 0.6 (stat) +/- 0.5 (syst) MeV via the decay mode B0_s -> D_s1(2536) mu nu X. A first measurement is made of the branching ratio product Br(b(bar) -> D_s1(2536) mu nu X).Br(D_s1(2536)->D* K0_S). Assuming that D_s1(2536) production in semileptonic decay is entirely from B0_s, an extraction of the semileptonic branching ratio Br(B0_s -> D_s1(2536) mu nu X) is made.
Exclusive semileptonic and nonleptonic decays of the Bc meson
2006
We study exclusive nonleptonic and semileptonic decays of the Bc-meson within a relativistic constituent quark model previously developed by us. For the nonleptonic decays we use the factorizing approximation. We update our model parameters by using new experimental data for the mass and the lifetime of the Bc meson and the leptonic decay constants of the D-meson. We calculate the branching ratios for a large set of exclusive nonleptonic and semileptonic decays of the $B_c$ meson and compare our results with the results of other studies. As a guide for further experimental exploration we provide explicit formulas for the full angular decay distributions in the cascade decays Bc^- => J/ps…
Semileptonic decays ofBcmesons into charmonium states in a relativistic quark model
2005
We use the framework of a relativistic constituent quark model to study the semileptonic transitions of the ${B}_{c}$ meson into $(\overline{c}c)$ charmonium states where $(\overline{c}c)={\ensuremath{\eta}}_{c}(^{1}S_{0})$, $J/\ensuremath{\psi}(^{3}S_{1})$, ${\ensuremath{\chi}}_{c0}(^{3}P_{0})$, ${\ensuremath{\chi}}_{c1}(^{3}P_{1})$, ${h}_{c}(^{1}P_{1})$, ${\ensuremath{\chi}}_{c2}(^{3}P_{2})$, $\ensuremath{\psi}(^{3}D_{2})$. We compute the ${q}^{2}$ dependence of all relevant form factors and give predictions for their semileptonic ${B}_{c}$ decay modes including also their $\ensuremath{\tau}$ modes. We derive a formula for the polar angle distribution of the charged lepton in the $(l{\ens…
The Isgur-Wise function from the lattice
1995
We calculate the Isgur-Wise function by measuring the elastic scattering amplitude of a $D$ meson in the quenched approximation on a $24^3\times48$ lattice at $\beta=6.2$, using an $O(a)$-improved fermion action. Fitting the resulting chirally-extrapolated Isgur-Wise function to Stech's relativistic-oscillator parametrization, we obtain a slope parameter $\rho^2=1.2+7-3. We then use this result, in conjunction with heavy-quark symmetry, to extract $V_{cb}$\ from the experimentally measured $\bar B\to D^*l\bar\nu\,$\ differential decay width. We find $|V_{cb}|\sqrt{\tau_B/1.48{\mathrm ps}}= 0.038 +2-2 +8-3, where the first set of errors is due to experimental uncertainties, while the second …
The Mach cone signal and energy deposition scenarios in linearized hydrodynamics
2010
Particle correlation measurements associated with a hard or semi-hard trigger in heavy-ion collisions may reflect Mach cone shockwaves excited in the bulk medium by partonic energy loss. This is of great interest because, when compared with theory, such measurements can provide information on the transport properties of the medium. Specifically, the formation of Mach cone shockwaves is sensitive to the viscosity and speed of sound, as well as the detailed nature of the jet medium interaction. However, modeling the physics of shockwave excitation to obtain a meaningful comparison with the measured correlations is very challenging since the correlations arise from an interplay of perturbative…
Measurement of the single-top-quark production cross section at CDF.
2008
We report a measurement of the single top quark production cross section in 2.2 ~fb-1 of p-pbar collision data collected by the Collider Detector at Fermilab at sqrt{s}=1.96 TeV. Candidate events are classified as signal-like by three parallel analyses which use likelihood, matrix element, and neural network discriminants. These results are combined in order to improve the sensitivity. We observe a signal consistent with the standard model prediction, but inconsistent with the background-only model by 3.7 standard deviations with a median expected sensitivity of 4.9 standard deviations. We measure a cross section of 2.2 +0.7 -0.6(stat+sys) pb, extract the CKM matrix element value |V_{tb}|=0…
"Table 11" of "Identified Charged Particles in Quark and Gluon Jets"
2003
No description provided.