Ciao Rob,
I don't understand completely what is your point: - that they should not claim any discrepancy because globally the agreement is fine - or that the final claim of 2.8 sigma global tension is wrong.
cheers, Francesco
On Tuesday 02 July 2013 09:33:44 Rob Lambert wrote: |Hi Again, | |Another way to think about it is to fit a Gaussian to the 24 data points, and |analyse whether one of them is an outlier or not. This is analytic given a |Gaussian distribution with one outlier and reduces to the Chebychev |inequality (or at least, I thought it did). | |Thanks, | |Rob | |------------------------------------------ |Robert Lambert |FOM-VU-NIKHEF-Bfys LHCb |Email: rob.lambert@cern.ch |------------------------------------------ |Nikhef N251 |Tel: +31 20 592 2131 |Fax: +31 20 592 5155 |------------------------------------------ |CERN, 13-1-018 |Tel: +41 22 767 4024 |Fax: +41 22 766 8109 |------------------------------------------ |________________________________ |From: bfys-physics-bounces@nikhef.nl [bfys-physics-bounces@nikhef.nl] on |behalf of Rob Lambert [Rob.Lambert@cern.ch] Sent: 02 July 2013 11:30 |To: Diego Martinez Santos; Marcel Merk |Cc: bfys-physics@nikhef.nl |Subject: Re: [Bfys-physics] B->K*mumu paper | |(24*0.0001*2) | ^ missed a zero .... | |Rob | |------------------------------------------ |Robert Lambert |FOM-VU-NIKHEF-Bfys LHCb |Email: rob.lambert@cern.ch |------------------------------------------ |Nikhef N251 |Tel: +31 20 592 2131 |Fax: +31 20 592 5155 |------------------------------------------ |CERN, 13-1-018 |Tel: +41 22 767 4024 |Fax: +41 22 766 8109 |------------------------------------------ |________________________________ |From: Rob Lambert |Sent: 02 July 2013 11:29 |To: Diego Martinez Santos; Marcel Merk |Cc: bfys-physics@nikhef.nl |Subject: RE: [Bfys-physics] B->K*mumu paper | |Hi Diego, | |Well, I'm 100% sure that's right because it's just 24*0.001*2, which is the |integrated probability for a two-sided Gaussian test, but the question isn't |"what's the probability of that happening" which is actually "1", because it |did actually happen, but "how many such deviations would you need to see |before you can invalidate the null hypothesis of no deviation", and this |number is given by Chebychev's equality... well, I thought it was, anyway. | |Thanks, | |Rob | |------------------------------------------ |Robert Lambert |FOM-VU-NIKHEF-Bfys LHCb |Email: rob.lambert@cern.ch |------------------------------------------ |Nikhef N251 |Tel: +31 20 592 2131 |Fax: +31 20 592 5155 |------------------------------------------ |CERN, 13-1-018 |Tel: +41 22 767 4024 |Fax: +41 22 766 8109 |------------------------------------------ |________________________________ |From: Diego Martinez Santos |Sent: 02 July 2013 11:17 |To: Rob Lambert; Marcel Merk |Cc: bfys-physics@nikhef.nl |Subject: RE: [Bfys-physics] B->K*mumu paper | | |(PS: 0.566 \pm 0.033. forgot the % of course) | |________________________________ |Dende: Diego Martinez Santos |Enviado: martes, 02 de xullo de 2013 11:16 |Ata: Rob Lambert; Marcel Merk |Cc: bfys-physics@nikhef.nl |Asunto: RE: [Bfys-physics] B->K*mumu paper | | |Hi | | | |I;ve just made quick toyMC, I get that the probability(maxSigma) > 3.7 for |experiments consisting | |of 24 measurements is 0.566 \pm 0.033. | | | | | |Voila the code (needs SetupUrania): | | | |from scipy import random as rnd |from Urania import * |AccessPackage("Bs2MuMu") | |from RTuple import * | | | |def do_set_of_experiments(N): | l = [] | for i in range(N): | l.append(abs(rnd.normal())) | l.sort() | l.reverse() | return l[0] | |def do_test(N, Nexp = 50000): | tup = RTuple("File_test",["maxSigma/F"]) | for i in range(Nexp): | tup.fillItem("maxSigma",do_set_of_experiments(24)) | tup.fill() | tup.close() | | | | | |Then you just call do_test(24) and analyse the produced Ntuple. | | | | | | | |Cheers; | | | |Diego | | | | | | | | | |________________________________ |Dende: bfys-physics-bounces@nikhef.nl [bfys-physics-bounces@nikhef.nl] en |nome de Rob Lambert [Rob.Lambert@cern.ch] Enviado: martes, 02 de xullo de |2013 10:53 |Ata: Marcel Merk |Cc: bfys-physics@nikhef.nl |Asunto: Re: [Bfys-physics] B->K*mumu paper | |Yes. Chebychev's inequality gives an estimate for how often a deviation this |large this should happen, and it seems to be perfectly within the realms of |probability, in fact it seems to be expected, and even two such deviations |would not be strange. | |Gerhard might want to correct me here, though... | |Cheers, | |Rob | |------------------------------------------ |Robert Lambert |FOM-VU-NIKHEF-Bfys LHCb |Email: rob.lambert@cern.ch |------------------------------------------ |Nikhef N251 |Tel: +31 20 592 2131 |Fax: +31 20 592 5155 |------------------------------------------ |CERN, 13-1-018 |Tel: +41 22 767 4024 |Fax: +41 22 766 8109 |------------------------------------------ |________________________________ |From: Marcel Merk [marcel.merk@nikhef.nl] |Sent: 02 July 2013 10:51 |To: Rob Lambert |Cc: bfys-physics@nikhef.nl |Subject: Re: [Bfys-physics] B->K*mumu paper | |Hi Rob, |Let me just clarify: you question the claim of 0.5%, is that correct? |just to make sure I understand which point you comment on. |cheers, |- Marcel | | |On 2 July 2013 10:06, Rob Lambert |<Rob.Lambert@cern.chmailto:Rob.Lambert@cern.ch> wrote: Erm, just some |statistical queries.. what about chebychev's inequality: | |http://en.wikipedia.org/wiki/Chebyshev%27s_inequality | |"No more than 1/k^{2} of the distribution's values can be more than k |standard deviations away from the mean" | |In this case it is 1/(3.7*3.7) which is 7%, and 24*7% is 1.75, so no more |than 1.75 of the observables should be this far away. One deviation this |large is perfectly expected from Chebychev's inequality. | |Thanks, | |Rob | |------------------------------------------ |Robert Lambert |FOM-VU-NIKHEF-Bfys LHCb |Email: rob.lambert@cern.chmailto:rob.lambert@cern.ch |------------------------------------------ |Nikhef N251 |Tel: +31 20 592 2131tel:%2B31%2020%20592%202131 |Fax: +31 20 592 5155tel:%2B31%2020%20592%205155 |------------------------------------------ |CERN, 13-1-018 |Tel: +41 22 767 4024tel:%2B41%2022%20767%204024 |Fax: +41 22 766 8109tel:%2B41%2022%20766%208109 |------------------------------------------ |________________________________ |From: bfys-physics-bounces@nikhef.nlmailto:bfys-physics-bounces@nikhef.nl |[bfys-physics-bounces@nikhef.nlmailto:bfys-physics-bounces@nikhef.nl] on |behalf of Marcel Merk [marcel.merk@nikhef.nlmailto:marcel.merk@nikhef.nl] |Sent: 01 July 2013 18:01 |To: bfys-physics@nikhef.nlmailto:bfys-physics@nikhef.nl |Subject: [Bfys-physics] B->K*mumu paper | |Dear bfys-physics friend, |This is to let you know that I collect comments to the paper below. |To stimulate you to read it: we claim that the probability that the |measurement is consistent with the Standard Model is only 0.5%. A local |discrepancy of 3.7 sigma is observed. | | LHCb PAPER-2013-037: | "Measurement of form factor independent observables | in the decay $B^0\to K^{*0}\mu^+\mu^-$" | Link : https://cds.cern.ch/record/1557918 | Deadline : 09-Jul-2013 | |best regards, |- Marcel | |_______________________________________________ |Bfys-physics mailing list |Bfys-physics@nikhef.nlmailto:Bfys-physics@nikhef.nl |https://mailman.nikhef.nl/mailman/listinfo/bfys-physics
--- Francesco Dettori Nikhef - VU
+31 20 592 2230 (Nikhef) +41 22 76 76284 (CERN)