Search results for "form factor"

Kl3Semileptonic Form Factor from (2+1)-Flavor Lattice QCD

2008

We present the first results for the ${K}_{l3}$ form factor from simulations with $2+1$ flavors of dynamical domain wall quarks. Combining our result, namely, ${f}_{+}(0)=0.964(5)$ with the latest experimental results for ${K}_{l3}$ decays leads to $|{V}_{us}|=0.2249(14)$, reducing the uncertaintity in this important parameter. For the $O({p}^{6})$ term in the chiral expansion we obtain $\ensuremath{\Delta}f=\ensuremath{-}0.013(5)$.

Quark and gluon form factors to four-loop order in QCD: TheNf3contributions

2017

We calculate the four-loop massless QCD corrections with three closed quark lines to quark and gluon form factors. We apply a novel integration by parts algorithm based on modular arithmetic and compute all relevant master integrals for arbitrary values of the space-time dimension. This is the first calculation of a gluon form factor at this perturbative order in QCD.

Heavy Quark Symmetry and weak decays of heavy baryons

2008

I give an account of the physics ideas that go into the formulating of Heavy Quark Symmetry (HQS) and use HQS ideas to discuss various aspects of the weak semileptonic decays of heavy baryons.

The SCET_II and factorization

2003

We reformulate the soft-collinear effective theory which includes the collinear quark and soft gluons. The quark form factor is used to prove that SCET$_{\rm II}$ reproduces the IR physics of the full theory. We give a factorization proof in deep inelastic lepton-hadron scattering by use of the position space formulation.

Heavy Baryon Transitions in a Relativistic Three-Quark Model

1996

Exclusive semileptonic decays of bottom and charm baryons are considered within a relativistic three-quark model with a Gaussian shape for the baryon-three-quark vertex and standard quark propagators. We calculate the baryonic Isgur-Wise functions, decay rates and asymmetry parameters.

Deuteron form factor measurements at low momentum transfers

2016

A precise measurement of the elastic electron-deuteron scattering cross section at four-momentum transfers of 0.24 fm−1 ≤ Q ≤ 2.7 fm−1 has been performed at the Mainz Microtron. In this paper we describe the utilized experimental setup and the necessary analysis procedure to precisely determine the deuteron charge form factor from these data. Finally, the deuteron charge radius rd can be extracted from an extrapolation of that form factor to Q 2 = 0.

Working group on hadron polarizabilities and form factors

1998

Form-factor-independent test of lepton universality in semileptonic heavy meson and baryon decays

2021

In the semileptonic decays of heavy mesons and baryons the lepton-mass dependence factors out in the quadratic $\cos^2\theta$ coefficient of the differential $\cos\theta$ distribution. We call the corresponding normalized coefficient the convexity parameter. This observation opens the path to a test of lepton universality in semileptonic heavy meson and baryon decays that is independent of form-factor effects. By projecting out the quadratic rate coefficient, dividing out the lepton-mass-dependent factor and restricting the phase space integration to the $\tau$ lepton phase space, one can define optimized partial rates which, in the Standard Model, are the same for all three $(e,\mu,\tau)$ …

Measurement of theB0→π−ℓ+νandB+→η(′)ℓ+νbranching fractions, theB0→π−ℓ+νandB+→ηℓ+νform-factor shapes, and determination of|Vub|

2011

We report the results of a study of the exclusive charmless semileptonic decays, B^+ → η^((′))l^+ν and B^0 → π^-l^+ν, undertaken with approximately 464 × 10^6 BB pairs collected at the Υ(4S) resonance with the BABAR detector. The analysis uses events in which the signal B decays are reconstructed with a loose neutrino reconstruction technique. We obtain partial branching fractions for B^+ → ηl^+ν and B^0 → π^-l^+ν decays in three and 12 bins of q^2, respectively, from which we extract the f_+(q^2) form-factor shapes and the total branching fractions B(B^+ → ηl^+ν)=(0.36 ± 0.05_(stat) ± 0.04_(syst))× 10^(-4) and B(B^0 → π^-l^+ν)=(1.42 ± 0.05_(stat) ± 0.07_(syst)) × 10^(-4). We also measure B…

‘‘Improved’’ lattice study of semileptonic decays ofDmesons

1995

We present results of a lattice computation of the matrix elements of the vector and axial-vector currents which are relevant for the semi-leptonic decays $D \rightarrow K$ and $D \rightarrow K^*$. The computations are performed in the quenched approximation to lattice QCD on a $24^3 \times 48$ lattice at $\beta=6.2$, using an $O(a)$-improved fermionic action. In the limit of zero lepton masses the semi-leptonic decays $D \rightarrow K$ and $D \rightarrow K^*$ are described by four form factors: $f^{+}_K,V,A_1$ and $A_2$, which are functions of $q^2$, where $q^{\mu}$ is the four-momentum transferred in the process. Our results for these form factors at $q^2=0$ are: $f^+_K(0)=0.67 \er{7}{8}$…