Search results for "Variant"
showing 10 items of 1267 documents
Study of exclusive semileptonic and nonleptonic decays ofBc−in a nonrelativistic quark model
2006
We present results for different observables measured in semileptonic and non-leptonic decays of the $B_c^-$ meson. The calculations have been done within the framework of a nonrelativistic constituent quark model. In order to check the sensitivity of all our results against the inter-quark interaction we use five different quark--quark potentials. We obtain form factors, decay widths and asymmetry parameters for semileptonic $B_c^-\to c\bar c$ and $B_c^-\to \bar B$ decays. In the limit of infinite heavy quark mass our model reproduces the constraints of heavy quark spin symmetry. For the actual heavy quark masses we find nonetheless large corrections to that limiting situation for some for…
A new state of hadronic matter at high density
1997
We propose in this article that if the chemical potential exceeds a critical value in dense hadronic medium, a first-order phase transition to a new state of matter with Lorentz symmetry spontaneously broken (in addition to the explicit breaking) takes place. As a consequence, light vector mesons get excited as ``almost'' Goldstone bosons. Since the light vector mesons dominantly couple to photons, the presence of these new vector mesons could lead to an enhancement in the dilepton production from dense medium at an invariant mass lower than the free-space vector-meson mass. We provide a low-energy quark model which demonstrates that the above scenario is a generic case for quark theories w…
Parton showers from the dipole formalism
2007
We present an implementation of a parton shower algorithm for hadron colliders and electron-positron colliders based on the dipole factorisation formulae. The algorithm treats initial-state partons on equal footing with final-state partons. We implemented the algorithm for massless and massive partons.
The CP-Conserving Direction
1998
A symmetry transformation is well defined in the case of an invariant theory, being the corresponding operator undetermined otherwise. However, we show that, even with CP violation, it is possible to determine the CP transformation by separating the Lagrangian of the Standard Model in a CP-conserving and a CP-violating part, in a unique way, making use of the empirically known quark mixing hierarchy. To order \lambda^3 for the Bd-system, the CP-conserving direction matches one of the sides of the (bd) unitarity triangle. We use this determination to calculate the rephasing invariant parameter \epsilon, which measures CP-mixing in the B0-B0bar system.
Measurement of the Branching Fractions ofB¯→D**ℓ−ν¯ℓDecays in Events Tagged by a Fully ReconstructedBMeson
2008
We report a measurement of the branching fractions of D**- decays based on 417 fb-1 of data collected at the (4S) resonance with the BABAR detector at the PEP-II e+e- storage rings. Events are selected by fully reconstructing one of the B mesons in a hadronic decay mode. A fit to the invariant mass differences m(D(*))-m(D(*)) is performed to extract the signal yields of the different D** states. We observe the D**- decay modes corresponding to the four D** states predicted by heavy quark symmetry with a significance greater than 5 standard deviations including systematic uncertainties.
Measurement of the Effective Weak Mixing Angle inpp¯→Z/γ*→e+e−Events
2015
We present a measurement of the fundamental parameter of the standard model, the weak mixing angle, in $p\bar{p}\rightarrow Z/\gamma^{*}\rightarrow e^{+}e^{-}$ events at a center of mass energy of 1.96 TeV, using data corresponding to 9.7 fb$^{-1}$ of integrated luminosity collected by the D0 detector at the Fermilab Tevatron. The effective weak mixing angle is extracted from the forward-backward charge asymmetry as a function of the invariant mass around the Z boson pole. The measured value of $\sin^2\theta_{\text{eff}}^{\text{$\ell$}}=0.23146 \pm 0.00047$ is the most precise measurement from light quark interactions to date, with a precision close to the best LEP and SLD results.
The Bc → J/ΨKD weak decay and its relation with the D*s0(2317) resonance
2016
We study the influence of the D * s 0 (2317) + resonance in the decay B c → J/ψKD . In this process, we consider that the B c meson decays first into J/ψ and the quark pair cs , and then the quark pair hadronizes into DK or D s η components. The final state interaction, generating the D * s 0 (2317) + resonance, is described by the chiral heavy meson unitary approach. With the parameters chosen in order to match the pole position of the D * s 0 (2317) + , we obtain the DK invariant mass distribution of the decay B c → J/ψDK , and also the rate for B c → J/ψD * s 0 (2317). We predict the ratio of these two magnitudes. This decay mechanism has not been measured yet, and it would provide insig…
SU(3) Analysis of $$p\overline p$$ Decays into Two Mesons
1985
The process \(p\overline p \to MM'\) is analyzed in terms of 8 SU(3) invariant amplitudes with definite charge conjugation properties. The amplitudes are constructed such that they either correspond to quark annihilation or rearrangement diagrams. For the C’-odd case the process \(p\overline p \to PS + PS\) is examined, whereas for the C’-even case the decay \(p\overline p \to PS + V\) is analyzed. It will be shown that for C’-odd both annihilation and rearrangement contribute, whereas rearrangement is dominant in the C’-even case.
Jarlskog-like invariants for theories with scalars and fermions
1994
Within the framework of theories where both scalars and fermions are present, we develop a systematic prescription for the construction of CP-violating quantities that are invariant under basis transformations of those matter fields. In theories with Spontaneous Symmetry Breaking, the analysis involves the vevs' transformation properties under a scalar basis change, with a considerable simplification of the study of CP violation in the scalar sector. These techniques are then applied in detail to the two Higgs-doublet model with quarks. It is shown that there are new invariants involving scalar-fermion interactions, besides those already derived in previous analyses for the fermion-gauge an…
Ds0*(2317)+in the decay ofBcintoJ/ψDK
2016
In this paper we study the relationship between the ${D}_{s0}^{*}(2317{)}^{+}$ resonance and the decay of the ${B}_{c}$ meson into $J/\ensuremath{\psi}DK$. In this process, the ${B}_{c}$ meson decays first into $J/\ensuremath{\psi}$ and the quark pair $c\overline{s}$, and then the quark pair hadronizes into $DK$ or ${D}_{s}\ensuremath{\eta}$ components, which undergo final state interaction. This final state interaction, generating the ${D}_{s0}^{*}(2317{)}^{+}$ resonance, is described by the chiral unitary approach. With the parameters which allow us to match the pole position of the ${D}_{s0}^{*}(2317{)}^{+}$, we obtain the $DK$ invariant mass distribution of the decay ${B}_{c}\ensuremath…