Inclusive beauty decays and the spectator model

Altarelli, Guido; Petrarca, S.

doi:10.1016/0370-2693(91)90332-k

Cited by 133 publications

(129 citation statements)

References 33 publications

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“…This result is considerably smaller than the theoretical prediction in the parton model, where BR SL ∼ 13-15% [2]. Furthermore 1/m 2 Q non-perturbative corrections cannot reduce the predicted BR SL below 12.5% [3].…”

Section: Introductionmentioning

confidence: 54%

“…BR SL = (12.0 ± 0.7 ± 0.5 +0.9 −1.2 ± 0.2)% on-shell scheme (11.3 ± 0.6 ± 0.7 +0.9 −1.7 ± 0.2)% MS scheme (2) Here the errors correspond to the uncertainties on m b , α s (M Z ), the renormalization scale µ and the other parameters present in the calculation. It may now seem that the discrepancy in the B semileptonic branching ratio has essentially disappeared.…”

Section: Introductionmentioning

confidence: 99%

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The chromomagnetic dipole operator and the B semileptonic branching ratio

1996

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We consider the possibility of having a large branching ratio for the decay b → sg coming from an enhanced Wilson coefficient of the chromomagnetic dipole operator. We show that values of BR(b → sg) up to ∼ 10% or more are compatible with the constraints coming from the CLEO experimental results on BR(B → X s γ) and BR(B → X s φ). Such large values can reconcile the predictions of both the semileptonic branching ratio and the charm counting with the present experimental results. We also discuss a supersymmetric model with gluino-mediated flavour violations, which can account for such large values of BR(b → sg).

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Section: Introductionmentioning

confidence: 54%

Section: Introductionmentioning

confidence: 99%

The chromomagnetic dipole operator and the B semileptonic branching ratio

1996

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“…where the following notations have been used: I 0 and I 2 are phase-space factors: [7]. With x c ≃ 0.08 one obtains…”

Section: General Methodologymentioning

confidence: 99%

Inclusive B decays as a QCD lab

Bigi¹

1996

Physics Letters B

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Phenomenological models of heavy flavour decays differ significantly in their predictions of global features of B c decays, like the B c lifetime or the relative weight of c → s and b → c transitions. The 1/m Q expansion which is directly based on QCD allows predictions on the pattern to be expected, namely τ (B c ) to lie well below 1 psec with c → s dominating over b → c and a reduced semileptonic branching ratio. Due to interference effects one also predicts a lower charm content in the final states of B c decays than naively anticipated. The numerical aspect of the predictions, however, has to be viewed with considerable caution since one cannot expect the 1/m c expansion to converge readily for ∆C = 1 transitions.

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“…At present, there appears to be a conflict between experiment and theory for fitting both the inclusive semileptonic branching ratio and the number of charmed hadrons per B decay [1][2][3][4][5][6][7][8], n c = 1 − B(b → no charm) + B(b → ccs ′ ) ≈ 1 + B(b → ccs ′ ) .…”

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Hadronization of

1995

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The b → ccs transition is usually believed to hadronize predominantly in B → X c D ( * )− s with the D ( * )− s originating from the virtual W . We demonstrate in a variety of independent ways that other hadronization processes cannot be neglected. The invariant mass ofcs has sizable phase-space beyond m D +m K . The rate for B → DD KX could be significant and should not be ignored as was done in previous experimental analyses. We estimate the number of charmed hadrons per B-decay, n c , to be ≈ 1.3 to higher accuracy than obtained in previous investigations. Even though n c is currently measured to be about 1.1, observing a significant B → DD KX would support n c ≈ 1.3. Many testable consequences result, some of which we discuss.Typeset using REVT E X 1 At present, there appears to be a conflict between experiment and theory for fitting both the inclusive semileptonic branching ratio and the number of charmed hadrons per B decay The prime indicates that the corresponding Cabibbo-suppressed mode is included. Experimentally the inclusive semileptonic BR has been measured accurately to be [9]and n c is measured as [9] n c = 1.10 ± 0.06 .A value of B(b → ccs ′ ) ≈ 0.1, suggested by Eqs.(1) and (3), would lead to a theoretical prediction of B(B → Xℓν) that is too large-i.e., inconsistent with its measured value (2).On the other hand, theory predicts n c ≈ 1.3 when the observed semileptonic BR is used as input, which is demonstrated below. Thus a conflict arises between (2) and ( Although this theoretical analysis hints that n c may be larger than currently measured [5][6][7]2,3], it is difficult to draw firm conclusions from this direct calculation of B(b → ccs ′ ) in view of the large uncertainties. 2It should also be stressed at this point, that the experimental determination of B(B → Xℓν) is reliable and accurate. In contrast, the measurement of n c is a sum over the inclusive yields of many charmed hadron species in B decays. It is thus prone to large uncertainties, perhaps larger than currently realized. Figure 1 displays the discrepancy graphically. We discuss now in some detail how the theoretical curve has been generated. Our objective is to draw the most accurate curve of n c versus semi-electronic BR with presently available theoretical calculations. We do not use the prediction for B(b → ccs ′ ) because it involves large errors, but rather proceed as follows. We start withwhere B(b → no charm) is small, typically at the percent level. We taketo account for the small fraction of b → s + no charm [10] and charmless b → u transitions.Furthermore we usewhich is in accordance with the result of Ref.[11] and also agrees with a recent ALEPH measurement [12],The last required ratio is Combining Eqs. (4), (5), (6), (8), the b → ccs ′ branching fraction can be written asIn this relation the very small contribution from b → ucs ′ transitions has been neglected.Eqs. (1) and (9) yield the number of charms per B decay aswhere we note that B(b → ccs ′ ) drops out in the linear relation between n c and B → X c e...

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Inclusive beauty decays and the spectator model

Cited by 133 publications

References 33 publications

The chromomagnetic dipole operator and the B semileptonic branching ratio

The chromomagnetic dipole operator and the B semileptonic branching ratio

Inclusive B decays as a QCD lab

Hadronization of

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