Hi guys,

here is a lot of inside information from Belle on their way to 
re-weight the D**lnu MC kindly provided by Elisabetta and Phill 
after a discussion I had with Elisabetta at Beauty06. Clearly, 
there is a bunch of things to digest.

Once we have fixed the SP5/SP6 bug there is certaintly additional 
room for improvements.

Cheers,
Heiko


---------- Forwarded message ----------
Date: Fri, 20 Oct 2006 06:55:25 +1000 (EST)
From: Phillip Urquijo <[log in to unmask]>
To: Heiko Lacker <[log in to unmask]>
Cc: "[log in to unmask]" <[log in to unmask]>
Subject: Re: D** re-weighting

Hello Heiko,

For the D** component of the MC we make use of 1/mQ corrections to the 
Isgur-Wise functions used to describe the differential decay rate of 
B->D** l nu,  given in: A.K.Leibovich, Z.Ligeti, I.W.Stewart, M.B.Wise, 
Phys. Rev. D57, 308(1998).  These models allow us to both; correct the w 
(the dot product of the four velocity of the B meson, and that of the 
recoiling D(
) meson) distributions of those produced using the Isgur-Wise functions in 
the MC, and to provide bounds on the less well known broad resonant 
branching fractions.  We use experimental constraints from the ratios:

R_(semileptonic) = BR(B->D1 l nu) / BR(B->D*2 l nu),  (mostly from 
hep-ex/0112028 )
R_(hadronic)       = BR(B->D1 pi) / BR(B->D*2 pi) (using factorisation) 
(K. Abe etal. BelleCollaboration, PRL94, 221805(2005): this paper also 
provides mass measurements of the D** components)

as well as BR(B -> D1 l nu) and limits on BR(B->D*2 l nu) (PDG).  There 
are 3 variables describing the corrections, which are additionally bound 
by theoretical arguments.  The differential decay rates are calculated for 
the components: D*0, D*1 (wide), and D1, D*2 (narrow).  There are five 
models discussed in the theory paper, split into two groups, A group 
(decay rates expanded in (w-1)), and B group (decay rates expanded in w). 
The difference between the expansions is suggested to provide an estimate 
of the theoretical uncertainty associated to the 1/mQ corrections.

We can determine bounds on the semileptonic ratios:
BR(B->D*1 l nu) / BR(B->D1 l nu),
BR(B->D*0 l nu) / BR(B->D1 l nu),
BR(B->D*2 l nu) / BR(B->D1 l nu),

Using these ratios in combination with BR(B -> D1 l nu), we determine the 
BR for the remaining D** components.  We check for consistency with 
BR(B->D(*)pi l nu) (D. Liventsev, T. Matsumoto et al, (The Belle 
Collaboration), published in PRD 72, 051109(R) (2005)) and full 
semileptonic rate measurements (HFAG), based on assumptions/measurements 
of D** ->D pi pi decay rates (see K. Abe etal. BelleCollaboration, PRL94, 
221805(2005)).

On a technical note, we used privately developed code by DELPHI (not 
written by the author) written in fortran, to perform the differential 
decay rate calculations.

Interestingly there are quite significant changes to the q^2 
distributions. ( w = ( mB^2 + mD(*)^2 - q^2 )/( 2 mB mD(*) ).

Let me know if you would like more information/references.

Best Regards,
Phillip Urquijo



On 19/10/2006, at 2:28 AM, Heiko Lacker wrote:

Hi,

some time ago I send you this email and maybe it was lost.
Quantitative information on this re-weighting would be very welcome.

Cheers,
Heiko

On Mon, 2 Oct 2006, Heiko Lacker wrote:

Hi Phill,

I had a chat with Elisabetta at Beauty06 about your D** re-weighting
procedure after I have seen how well the MC describes the mX spectrum
measured in Belle's moment's analysis of B-Xclnu.
She told me that I can contact you to get quantitative details about
how the D** part of the MC has been re-weighted. I would appreciate
any further insight in what has been done.

Cheers,
Heiko