arXiv subjects

Fabrizio Gabbiani

Publications and source records attributed to Fabrizio Gabbiani.

12 recordsLinked to original sources

arXiv2009

Lifetime difference in B_s mixing: Standard Model and beyond

We present a calculation of $1/m_b^2$ corrections to the lifetime differences of $B_s$ mesons in the heavy-quark expansion. We find that they are small to significantly affect $ΔΓ$ $(B_s)$ and present the result for lifetime difference including non-perturbative $1/m_b$ and $1/m_b^2$ corrections. We also analyze the generic $ΔB$ = 1 New Physics contributions to the lifetime difference of $B_s$ mesons and provide several examples

hep-ph↗

arXiv2007

Lifetime Difference in B_s mixing: Standard Model and beyond

We present a calculation of 1/m^2_b corrections to the lifetime differences of B_s mesons ΔΓ_s in the heavy-quark expansion. We find that they are small to significantly affect ΔΓ_s and present the result for lifetime difference including non-perturbative 1/m_b and 1/m_b^2 corrections. We also analyze the generic ΔB = 1 New Physics contributions to ΔΓ_s and provide several examples.

hep-ph↗

arXiv2006

Heavy Meson Molecules in Effective Field Theory

We consider the implications from the possibility that the recently observed state X(3872) is a meson-antimeson molecule. We write an effective Lagrangian consistent with the heavy-quark and chiral symmetries needed to describe X(3872). We explore the consequences of the assumption that X(3872) is a molecular bound state of D^{*0} and anti-D^0 mesons for the existence of bound states in the D^0-anti-D^0 and D^{*0}-anti-D^{*0}.

hep-ph↗

arXiv2005

X(3872): Hadronic Molecules in Effective Field Theory

We consider the implications from the possibility that the recently observed state X(3872) is a meson-antimeson molecule. We write an effective Lagrangian consistent with the heavy-quark and chiral symmetries needed to describe X(3872). We claim that if X(3872) is a molecular bound state of D^*0 and anti-D^0 mesons, the heavy-quark symmetry requires the existence of the molecular bound state X_b of B^*0 and anti-B^0 with the mass of 10604 MeV.

hep-ph↗

arXiv2004

Spectator effects and lifetimes of heavy hadrons

We present a calculation of subleading 1/m_b corrections to spectator effects in the ratios of beauty hadron lifetimes in heavy-quark expansion. We find that these effects are sizable and should be taken into account in systematic analyses of heavy hadron lifetimes. In particular, the inclusion of 1/m_b corrections brings into agreement the theoretical predictions and experimental observations of the ratio of lifetimes of Λ_b-baryon and B_d meson. We obtain τ(B_u)/τ(B_d) = 1.06 \pm 0.02, τ(B_s)/τ(B_d)= 1.00 \pm 0.01, τ(Λ_b)/τ(B_d)= 0.86 \pm 0.05.

hep-ph↗

arXiv2003

Lambda_b lifetime puzzle in heavy-quark expansion

Lifetime differences of heavy hadrons can be consistently computed in heavy-quark expansion. The leading effects appear through spectator interactions at order 1/m_b^3. We compute a well-defined subset of 1/m_b^4 corrections to the lifetime ratio of Lambda_b baryon and B_d meson. We find that these corrections are large and should be taken into account in the systematic analysis of heavy hadron lifetimes. We claim that they could shift the ratio τ_{Λ_b}/τ_{B_d} by as much as -4.5%, significantly reducing the discrepancy between the theoretical predictions and experimental observations.

hep-ph↗

arXiv2001

Reanalysis of the decay K_L -> pi0 e+ e-

The decay K_L -> pi0 e+ e- is being searched for as a signal of direct Delta S = 1 CP violation. We provide a thorough updating of the analysis of the three components of the decay: 1) Direct CP violation, 2) CP violation through the mass matrix and 3) CP-conserving (two-photon) contributions. First the chiral calculation of the K_S -> pi0 e+ e- rate, due to Ecker, Pich and de Rafael (EPR), is updated to include recent results on the nonleptonic amplitude. Then we systematically explore the uncertainties in this method. These appear to be so large that they will obscure the direct CP violation unless it is possible to measure the K_S -> pi0 e+ e- rate. The CP-conserving amplitude remains somewhat uncertain, but present indications are such that there may be a sizable CP-violating asymmetry in the e+, e- energies from the interference of the CP-conserving and CP-violating amplitudes and this may potentially be useful in determining whether direct CP violation is present.

hep-ph↗

arXiv2000

Higher Partial Waves in an Effective Field Theory Approach to nd Scattering

The phase shifts for the higher partial waves (l\ge 1) in the spin quartet and doublet channel of nd scattering at centre-of-mass energies up to 15 MeV are presented at next-to-leading and next-to-next-to-leading order in an effective field theory in which pions are integrated out. As available, the results agree with both phase shift analyses and potential model calculations.

nucl-th↗

arXiv1999

Rare Kaon Decays and CP Violation

Rare kaon decays are an important testing ground of the electroweak flavor theory: They can provide new signals of CP-violating phenomena. The interplay of long-distance QCD effects in strangeness-changing transitions can be analyzed with Chiral Perturbation Theory techniques. In particular, two rare kaon decays are analyzed: The first decay, K_L -> pi0 e+e-, is being searched for as a signal of direct Delta S = 1 CP violation. We provide a thorough updating of the analysis of the three components of the decay: 1) Direct CP violation, 2) CP violation through the mass matrix and 3) CP-conserving (two-photon) contributions. First the chiral calculation of the K_S -> pi0 e+e- rate is updated to include recent results on the nonleptonic amplitude. Then we systematically explore the uncertainties in this method. The CP-conserving amplitude remains somewhat uncertain, but present indications are such that there may be a sizable CP-violating asymmetry in the e+, e- energies from the interference of CP-conserving and CP-violating amplitudes. This may potentially be useful in determining whether direct CP violation is present. The second decay, K_L -> pi0 gamma e+e-, which occurs at a higher rate than the nonradiative process K_L -> pi0 e+e-, can be a background to CP violation studies using the latter reaction. The leading order chiral loop contribution to K_L -> pi0 gamma e+e- is completely calculable.

hep-ph↗

arXiv1999

Unitarity corrections to K+ -> pi+ gamma l+l-

We perform a chiral one-loop calculation of the unitarity corrections to the processes K+ -> pi+ gamma l+l- up to O(E^6), taking into account pi+pi- intermediate states. Branching ratios and differential branching ratios are computed and presented to demonstrate the importance of the above corrections.

hep-ph↗

arXiv1998

Chiral predictions for K_L -> pi0 gamma mu+ mu-

We have previously analysed the chiral predictions for the decay K_L -> pi0 gamma e+ e- and discussed how experimental measurements of this process can help our understanding of chiral theories and of CP tests. Motivated by the possibility that the analogous muonic process may soon be measurable, we extend this calculation to the decay K_L -> pi0 gamma mu+ mu-. Branching ratios and differential branching ratios are calculated and presented. Measurements of these will help shed some light on the puzzles in our understanding of the chiral loop effects which were raised by the rate for K_L -> pi0 gamma gamma.

hep-ph↗

arXiv1997

K_L -> pi0 gamma e+ e- and its relation to CP and chiral tests

The decay K_L -> pi0 gamma e+ e- occurs at a it higher rate than the nonradiative process K_L -> pi0 e+ e-, and hence can be a background to CP violation studies using the latter reaction. It also has an interest in its own right in the context of chiral perturbation theory, through its relation to the decay K_L -> pi0 gamma gamma. The leading order chiral loop contribution to K_L -> pi0 gamma e+ e-, including the [q(e+) + q(e-)]^2/m^2(pi) dependence, is completely calculable. We present this result and also include the higher order modifications which are required in the analysis of K_L -> pi0 gamma gamma.

hep-ph↗