1,721,050 research outputs found
Extracting |<i>V<sub>ub</sub></i>| From Omnès dispersion relations and lattice QCD
No full textDispersion approaches offer a way to use directly calculated/measured form-factor values from exclusive semileptonic B → π decays to constrain the overall q2-shape of the form-factor(s). This can make the determination of |Vub| from exclusive decays competitive with that from inclusive decays. Here we consider the use of Omnès dispersion relations for this purpose
Elastic s-wave scattering phase shifts and |Vub| from lattice calculations of form factors for exclusive semileptonic decays
No full textOmnès dispersion relations make a connection between form factors for exclusive semileptonic decays and phase shifts in the corresponding elastic scattering channels. We describe two applications. In the first, we use lattice form factor calculations to learn about phase shifts in elastics-wave isospin-1/2 channels for Kπ , Bπ , Dπ and DK scattering. The aim of the second application is to make the determination of the CKM matrix element magnitude |Vub| from exclusive semileptonic B → π decays competitive with that from inclusive decays. Here we use many subtractions in an Omnès dispersion relation to motivate a simple fitting function, allowing data to constrain the q2 shape of the differential decay rate and theory, primarily lattice results, to provide normalisation via form factor values
Semileptonic bc to cc Baryon Decay and Heavy Quark Spin Symmetry
No full textWe study the semileptonic decays of the lowest-lying bc baryons to the lowest-lying cc baryons
(b0c ! cc and 0 bc ! cc), in the limit mb;mc QCD and close to the zero-recoil point. The
separate heavy quark spin symmetries make it possible to describe all these decays using a single form
factor. We recover results derived previously by White and Savage in a manner which we think is more
straightforward and parallels the method applied later to study Bc semileptonic decays. We further discuss
the resemblance between the bc baryon decays and those of Bc mesons to c and J= mesons and
comment on the relation between the slopes of the single functions describing each set of decays. Our
results can straightforwardly be applied to the decays of bb baryons to bc baryons
B0(s)- B0(s) mixing and b hadron lifetimes from lattice QCD
No full textWe discuss neutral Bs,d meson mixing and b-hadron lifetimes from the perspective of recent lattice calculations. In particular, we consider matrix elements which can be combined with measured ?Ms,d to constrain |Vtd|, the lifetime ratios ?(?b)/?(B0d) and ?(B-)/?(B0d) and the lifetime difference, ??Bs/?Bs, in the neutral Bs meson system
Data for Thesis " and decays in the Continuum Limit of Lattice QCD"
No full textDataset to support Southampton Doctoral Thesis " and decays in the Continuum Limit of Lattice QCD"
The data files are all in the HDF5 format. These can be viewed using the standard HDF5 command-line tools such as h5dump, or opened with reader libraries such as the h5py Python library.
There are three important datasets in each HDF5 file under the root group:
- central: The timeslice-by-timeslice mean of the raw data.
- bs_mean: The timeslice-by-timeslice mean of the Bootstrap samples.
- samples: The Bootstrap samples in a (Configurations X Timeslices)-shaped matrix.
This dataset contains, for the two processes BtoPi and BstoK:
- data/
The full set of 2pt and 3pt correlators used to extract form factors across square lattice momenta n^2=0,1,2,3,4 and across the six ensembles C1, C2, M1, M2, M3, and F1S.
- B/Bs naming convention: [B/Bs]-[ensemble]-[momentum]-[num_smeared].h5 (where num_smeared=0 -> PointPoint, =1 -> PointSmear, =2 -> SmearSmear)
- K/Pi naming convention: [Pi/K]-[ensemble]-[momentum].h5
- 3pt naming convention: [B/Bs]to[Pi/K]_3pt_[t/i]-[ensemble]-[momentum]
- box/
The additional correlators required for the RHQ parameter "box" systematic analysis on the C1 and M2 ensembles. Final-state correlators are duplicates of the ones in the 'data/' directory.
- B/Bs naming convention: [B/Bs]-[ensemble]-[m_b]-[csw]-[zeta]-[momentum]-[num_smeared].h5 (where num_smeared=0 -> PointPoint, =1 -> PointSmear, =2 -> SmearSmear)
- K/Pi naming convention: [Pi/K]-[ensemble]-[momentum].h5
- 3pt naming convention: [B/Bs]to[Pi/K]_3pt_[t/i]-[ensemble]-[m_b]-[csw]-[zeta]-[momentum]
- strange/ (BstoK only)
The additional correlators required for the strange-quark mistuning systematic analysis on the C1 ensemble.
- B/Bs naming convention: [B/Bs]-[ensemble]-[m_s]-[m_b]-[csw]-[zeta]-[momentum]-[num_smeared].h5 (where num_smeared=0 -> PointPoint, =1 -> PointSmear, =2 -> SmearSmear)
- K/Pi naming convention: [Pi/K]-[ensemble]-[m_s]-[momentum].h5
- 3pt naming convention: [B/Bs]to[Pi/K]_3pt_[t/i]-[ensemble]-[m_s]-[m_b]-[csw]-[zeta]-[momentum]</span
WG2 conveners' report: Vtd and Vts, B-Bar mixing, radiative penguin and rare (semi)leptonic decays
No full textWe introduce the Working Group 2 proceedings contributions from the 2nd workshop on the CKM Unitarity Triangle and note their connection to the proceedings of the first workshop. The topic of WG2 was the determination of the CKM matrix elements Vtd and Vts from B-Bbar mixing, radiative penguin B to X{s/d} gamma decays and rare (semi)leptonic decays such as B to Xs l+ l-.<br/
Elastic s-wave B pi, D pi, D K and K pi scattering from lattice calculations of scalar form factors in semileptonic decays
No full textWe show how theoretical, principally lattice calculations of the scalar form factors in semileptonic pseudoscalar-to-pseudoscalar decays can be used to extract information about the corresponding elastic s-wave scattering channels. We find values for the scattering lengths mpia=0.179(17)(14), 0.26(26) and 0.29(4) for elastic s-wave isospin-1/2 Kpi, Bpi and Dpi channels, respectively. We also determine phase shifts. For the DK channel we find hints that there is a bound state which can be identified with the recently discovered Ds0+(2317)
Extracting |V(ub)| from B -> pi l nu decays using a multiply-subtracted Omnes dispersion relation
No full textWe use a multiply-subtracted Omnès dispersion relation for the form factor f+ in B-->pi semileptonic decay, allowing the direct input of experimental and theoretical information to constrain its dependence on q2, thereby improving the precision of the extracted value of |Vub|. Apart from these inputs we use only unitarity and analyticity properties. We obtain |Vub|=(4.02±0.35)×10-3, improving the agreement with the value determined from inclusive methods, and competitive in precision with them
Hadronic form factors for rare semileptonic <i>B</i> decays
No full textWe discuss first results for the computation of short distance contributions to semileptonic form factors for the rare decays and . Our simulations are based on RBC/UKQCD's ensembles with domain wall light quarks and the Iwasaki gauge action. For the valence -quark we chose the relativistic heavy quark action
Form factor curves consistent with unitarity for semileptonic decays
No full textWe discuss a method to generate form factor curves consistent with dispersive constraints across the entire kinematic range for exclusive semileptonic (SL) pseudoscalar to pseudoscalar decays, for example B→πℓνB→πℓν and B_s \rightarrowK \ell \nu. The work builds on the Dispersive Matrix (DM) method which allows model-independent extrapolation to any desired q2q2value in the SL physical region using known form factor information at specific discrete q2q2 points as input. Here qq is the outgoing lepton-pair 4-momentum. An obstacle in using DM results for phenomenological predictions, such as forward-backward asymmetries,is that it is not obvious how to use the bounds over continuous ranges of q2q2 when integrating, for example, the differential decay rate over the physical q2q2 range or over bins in q2q2. We describe a method to generate a family of curves, each consistent with unitarity constraints, that can be used in the same way as aset generated from a parametrized fit (e.g. a zz-fit). This allows integration over any desired bins. We further show some techniques to increase the computational efficiency of the method. We emonstrate the application to determining ∣Vub∣∣Vub∣
- …
