Hi Kristof,

Only a few comments on the paper from my side (a few repeating what we said this morning).

Cheers, Niels

Abstract * [It is surprising that the systematic error is two times smaller for the Bs0->D-Ds+ lifetime. How comes?]

L.102 [Kristof, I would keep this sentence with 97% and 33%, because the fact that you cut the background with an additional factor 3 can be interesting.]

L.149 [Add a sentence where you say why the B- normalization is preferred over the B0 normalization channel.]

Fig.1 [Add label inside plot: 'LHCb simulation']

Fig.3 [Add label 'LHCb']

Fig.3 [You assumed tau=1.5 ps when defining the bin centres; how large is the effect on your measurement if you would assume tau=1.25 ps?]

Fig.4 [Make font of legend non-bold]

[Just a warning: the PRL justification seems not asked for by PRL anylonger.]

On Thu, 7 Nov 2013, Tjeerd Ketel wrote:

On Thu, 31 Oct 2013, Tjeerd Ketel wrote:

...

Dear colleagues,

Bfys Meeting Friday 8 November in N328 and Vidyo

9:30 - 9:55 Staff meeting (only permanent staff) 10:00 - 10:50 "Introduction and discussion of LHCb-PAPER-2013-060: Measurement of the B0s(bar) to Ds+ Ds- and B0s(bar) to D- Ds+ effective lifetimes" by Kristof de Bruyn

The presentation can be found at http://agenda.nikhef.nl/conferenceDisplay.py?confId=2622 and will be protected by lhcb, etc.

Vidyo link in Nikhef Bfys Meeting (at Institutes->Nikhef of Friday 21 June 2013) https://indico.cern.ch/conferenceDisplay.py?confId=255991 protected by PIN 1328.

Best regards, Tjeerd

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Hi Kristof,

Thanks again for following up. I had a look at his replies. From my part, I am happy with most of them, but I am not satisfied with his reply on Gamma_L.

My replies are in black:

(3) You write (Line 75) that you have loose PID requirements which are >95% efficient. That is difficult to understand. Looking at the ANA note we see that the efficiency ratio of Bd over Bs is about 0.7, while the only difference between the two modes is the PID efficiency of a single kaon versus pion. Why is this ratio not closer to 1?

--> There is a cut on the D+ lifetime at 1.0 ps, so that the average decay length of the D+ is comparable to the Ds+. This is the main reason. There are also O(10%)-ish differences in geometric acceptance, and these are not included in the plot, since they only introduce an offset, which is irrelevant in the analysis. The relative geometric efficiencies for the Bs->DsDs modes ARE accounted for though.

A similar question can be asked about Fig 1. This ratio is about 1.7, which can be partially explained by the additional kaon in the Bs->DsDs mode, but not fully (the efficiency to reconstruct an additional particle is about 70-80%). Could you explain this effect?

--> It is because the efficiency to reconstruct an extra particle is not 20-30% for multi-body decays. It is well known by many in the B2OC group that an extra particle loses you about a factor of 2-3, depending on decay mode. I don't know where you get your numbers from, but they are not correct for these modes.

The cut on the D+ lifetime is not mentioned in the text. Please put this number in the paper. The factor 2-3 in single-particle efficiency loss is only when you apply PID cuts. Without such cuts the loss is at the 30% level.

Abstract: If Gamma_L is just 1/tau_eff then there is really no need to put this number in the abstract. Please consider removing that line. --> Prefer to keep it.

There is no need to quote two identical numbers. Especially not in the abstract!

If you want to give a results for Gamma_L (not in the abstract) then write explicitly under which assumptions for phi_s this is. -> I think this is too much detail for the abstract. If I include phi_s assumptions, then I need to define phi_s. I don't think it is needed.

Sorry, but you misunderstood. Gamma_L does not belong in the abstract indeed. The point is that when quoting Gamma_L in the results section of the main text (line 175-176), you need to mention the EXACT assumptions.

Cheers Jeroen

On 12 Nov, 2013, at 17:50 pm, Kristof De Bruyn <debkr@nikhef.nlmailto:debkr@nikhef.nl> wrote:

Dear all,

Steve has already replied to our comments. See http://cds.cern.ch/record/1627619

I am not yet happy with (at least) his answer to my first question, so I will get in touch with him. If there are other points you are not satisfied with, please let me know asap.

Could somebody with more experience also have a look at his reply to question 5? I can't judge ... The assumption is the main reason why the systematic error on Bs->D-Ds is only half that of Bs->DsDs, something that is a priori surprising.

Cheers, Kristof

Quoting Kristof De Bruyn debkr@nikhef.nl:

Dear all,

I am collecting the comments from Nikhef on LHCb-PAPER-2013-060: "Measurement of the B0s(bar) to Ds+ Ds- and B0s(bar) to D- Ds+ effective lifetimes". So far I have already received comments from Jeroen van Tilburg, and from Niels. If there are no objections, I will post the attached list to CDS tonight (Deadline is tomorrow, November 12th).

Cheers, Kristof

Quoting Tjeerd Ketel tjeerd@nikhef.nl:

Dear colleagues,

Bfys Meeting Friday 8 November in N328 and Vidyo

9:30 - 9:55 Staff meeting (only permanent staff) 10:00 - 10:50 "Introduction and discussion of LHCb-PAPER-2013-060: Measurement of the B0s(bar) to Ds+ Ds- and B0s(bar) to D- Ds+ effective lifetimes" by Kristof de Bruyn

The presentation can be found at http://agenda.nikhef.nl/conferenceDisplay.py?confId=2622 and will be protected by lhcb, etc.

Vidyo link in Nikhef Bfys Meeting (at Institutes->Nikhef of Friday 21 June 2013) https://indico.cern.ch/conferenceDisplay.py?confId=255991 protected by PIN 1328.

Best regards, Tjeerd

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Dear all,

For those of you still following the discussion on Bs->DsDs: the next chapter can be found at https://cds.cern.ch/record/1629276

Cheers, Kristof

Quoting Kristof De Bruyn debkr@nikhef.nl:

Dear all,

Steve has already replied to our comments. See http://cds.cern.ch/record/1627619

I am not yet happy with (at least) his answer to my first question, so I will get in touch with him. If there are other points you are not satisfied with, please let me know asap.

Could somebody with more experience also have a look at his reply to question 5? I can't judge ... The assumption is the main reason why the systematic error on Bs->D-Ds is only half that of Bs->DsDs, something that is a priori surprising.

Cheers, Kristof

Quoting Kristof De Bruyn debkr@nikhef.nl:

...

Dear all,

I am collecting the comments from Nikhef on LHCb-PAPER-2013-060: "Measurement of the B0s(bar) to Ds+ Ds- and B0s(bar) to D- Ds+ effective lifetimes". So far I have already received comments from Jeroen van Tilburg, and from Niels. If there are no objections, I will post the attached list to CDS tonight (Deadline is tomorrow, November 12th).

Cheers, Kristof

Quoting Tjeerd Ketel tjeerd@nikhef.nl:

...

Dear colleagues,

Bfys Meeting Friday 8 November in N328 and Vidyo

9:30 - 9:55 Staff meeting (only permanent staff) 10:00 - 10:50 "Introduction and discussion of LHCb-PAPER-2013-060: Measurement of the B0s(bar) to Ds+ Ds- and B0s(bar) to D- Ds+ effective lifetimes" by Kristof de Bruyn

The presentation can be found at http://agenda.nikhef.nl/conferenceDisplay.py?confId=2622 and will be protected by lhcb, etc.

Vidyo link in Nikhef Bfys Meeting (at Institutes->Nikhef of Friday 21 June 2013) https://indico.cern.ch/conferenceDisplay.py?confId=255991 protected by PIN 1328.

Best regards, Tjeerd

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