Flavour Physics at SuperB Factory with Polarized Beam

1. EW Physics at a SuperBFlavour Factory with Polarized Beam and status of some Flavour Physics with Taus J. Michael Roney University of Victoria III Prometeo Workshop IFIC 16 November 2010

2. EW physics at LEP & SLC SLC machine and SLD J.Michael Roney

3. EW physics at LEP & SLC at LEP: 15M hadronic Z decays, unpolarised at SLC: 0.5M hadronic Z decays, polarisede- at SuperB: Z-term ~30M hadronic Z, polarised J.Michael Roney

4. EW physics at LEP & SLC J.Michael Roney

5. EW physics at LEP & SLC Asymmetries at Z-pole from measured cross-sections: correcting back to 100% pol J.Michael Roney

6. EW physics at LEP & SLC AFB for leptons and bl events at LEP J.Michael Roney

7. EW physics at LEP & SLC AFB for leptons at SLC AFB for b events (decay vertex charge) at SLC J.Michael Roney

8. EW physics at LEP & SLC Also Measure Polarisation in the final state at LEP J.Michael Roney

9. EW physics at LEP & SLC J.Michael Roney

10. EW physics at LEP & SLC comparing only ALR and A0,bfb 3.2σ J.Michael Roney

11. EW physics at LEP & SLC 2.8σ J.Michael Roney

12. EW physics at LEP & SLC J.Michael Roney

13. EW physics at LEP & SLC If AFBb is omitted from the SM fit MHiggs=76±5433 i.e a low mass Higgs is strongly preferred

14. EW physics at LEP & SLC from M. Chanowitz,arXiv:0806.0890 hep-ph J.Michael Roney

15. EW physics at SuperB at SuperB: g-Z interference term dominates over pure Z-exchange J.Michael Roney

16. A m-pair selection in BaBar • Efficiency = 53.4% • Purity = 99.6% • Projected no. of selected mu-pair events at SuperB for 75/ab is 45.6 billion expected stat. error on ALR= 4.6x10-6 Z. Yun thesis 2005

17. e+e-m+m- @ √s=10.58GeVScales as s The interference term is (nearly) everything - ALR interference term ~ gAegVm

18. Polarised Beams provide an impressive Precision EW Programme at SuperB polarised beam provide measurement of sin2Θw(eff) of using muon pairs of comparable precision to that obtained by SLD, except at 10.58GeV Similar measurement can be made with taus and charm Test neutral current universality at high precision Because it depends on gamma-Z interference it is sensitive to Z’ Measure NC Z-b-bbar vector coupling with higher precision and different systematic errors than determined at LEP with AFBb and at high precision J.Michael Roney

19. e+e- m+m- @ √s=10.58GeV expected stat. error on ALR = 4.6x10-6 sALR =5x10-6s(sin2qeff) = 0.00018 measured at 10.58GeV, run to Mz cfSLC ALRs(sin2qeff)= 0.00026 at Mz • Would be most precise measurement: • precision test of running to low √s • relative stat. error of 1.1% (pol=80%) • require ~0.5% systematic error on beam polarisation J.Michael Roney

20. Comments on Beam Polarization Systematic Errors at SLC (thanks for discussions with Peter Rowson – SLD/SLD SLAC) 1) The left-right luminosity asymmetry must there be controlled to the level of the stat error (10-6).  At the SLC, able to monitor this asymmetry (using various beamline instruments) to a precision of ~ 0.5x 10-4.   One needs two orders of magnitude improvement here. 2) SLC needed to experimentally limit the level of accidental positron polarization - which was done at the SLC to the 7 x 10-4 level.  In principle, this too would have to be improved by two orders of magnitude, but in a storage ring perhaps this effect might be expected theoretically to be very much smaller and not an issue.3) SLC able to completely ignore left-right asymmetric effects in the SLD detector efficiency at the SLC where ALR was ~10% (These effects that cause the response of the detector to a fermion at a given polar angle to differ from the response to an anti-fermion at the same polar angle).  When effects at the part per million level are relevant, this issue would have to be re-examined.  Perhaps this is still OK. J.Michael Roney

21. Comments on Beam Polarization Systematic Errors at SuperB • The L-R luminosity asymmetry is the most important and has to be controlled. • This can likely be achieved with good luminosity monitoring using Bhabhas. Some thought needed to go into this. J.Michael Roney

22. Similar approach for taus and electrons Will give most precise NC universality measurements All error ellipses would be only slightly larger than red electron ellipse J.Michael Roney

23. What of Z - b-bar couplings? • g-Z interferometry at the Phi factory (hep-ph/9512424 (Bernabeu, Botella,Vives) • Assuming only resonance production • Same arguments for ϒ(4S) (ignoring non-4S open beauty) J.Michael Roney

24. Z - b-bar couplings J.Michael Roney

25. next two slides courtesy of Oscar Vives BOTTOM LINE: work concludes that ALR from BBbar events at the 4S giving access to the Z-b-bbar vector coupling is indeed sound and in fact very robust! INDEPENDENT of whether via Continuum or Resonance J.Michael Roney

26. J.Michael Roney

27. slides from Oscar Vives J.Michael Roney

28. SM expectation & LEP Measurement of gVb • SM: -0.34372 +0.00049-.00028 • AFBb: -0.3220±0.0077 • with 0.5% polarization systematic and 0.3% stat error, SuperB can have an error of ±0.0021 J.Michael Roney

29. SM expectation & LEP Measurement of gVb • SM: -0.34372 +0.00049-.00028 • AFBb: -0.3220±0.0077 • with 0.5% polarization systematic and 0.3% stat error, SuperB can have an error of ±0.0021 J.Michael Roney

30. At SuperB no QCD corrections • At LEP QCD corrections were required – hadronization effects, hard gluons, etc • We think it was done properly with correctly assessed systematic uncertainties, but… • Real advantage at SuperB over a high energy machine, e.g. Z-factory, is that these corrections do not exist: we are coupling to pseudoscalarswith no hadronization J.Michael Roney

31. Similar approach can be used for Charm • Operate at a ccbar vector resonance above open charm threshold psi(3770) • If we want to get charm in the same way, need to have polarization at lower energies with sufficient luminosity • Alternatively, use 4S data and deal with hadronization J.Michael Roney

32. What if unpolarized beams? • Can still access some information for e+e- m+m-via AFB but very difficult: • Competition with AFB from QED box diagram • Need to control real detector FB charge asymmetries: note that at LEP the smallest systematic error achieved on AFB was 0.0005, this would translate into an unacceptably large error on sin2ϑeffW • other errors arise, e.g. boost J.Michael Roney

33. What if unpolarized beams? • Can’t directly access Z-b coupling from AFB : Y(4s) decays to pseudoscalars, so no sensitivity • Proposal to measure at Y(3S) via tau polarization where tau-pairs are produced in decay of Y(3S) (Bernabeu, Botella, Vives, Eur.Phys.J.C7:205-215,1999. ) • In principle, very nice idea. In practice, need: to: • Run at Y(3S) • Need precise determination of continuum to Y(3S) production rate: so need equal amount of off-resonance data • Then, deal with backgrounds &tc…. J.Michael Roney

34. Neutral Current Physics Programme • Measure sin2ϑeffW at 10.58GeV with ALR • Competitive precision EW measurements • with muon – probe running, NuTeV result • with muons and taus – probe NC universality at low Q2 • with charm • with b’s: probe residual 3σ effect from LEP AFB • Start to consider L-R luminosity and other systematic errors • Z’ limits etc that we can achieve J.Michael Roney

35. The polarization is initially motivated by searches for NP in taus, but precision EW measurements represent a new ‘killer app’ • e.g. tau EDM with polarization ~7-10x10-20e-cm cf 17 – 34x10-20e-cm without polarization BACKGROUND SUPPRESSION TOOL Disentangle NP model with LFV discovery J.Michael Roney

36. Shifting gear: standard model's flavour sector ~two dozen fundamental SM parameters • Couplings of EW and strong interactions • Weak mixing angle, Z boson mass • Masses of quarks and leptons • Matrix characterizing the mixing of weak and mass eigenstates of quarks and, recently in extended SM, leptons • Higgs mass, strong-CP angle Heavy flavour sector primarily touches on the Cabibbo-Kobayashi-Maskawa (CKM) matrix J.Michael Roney

37. W- qi qj GFVij CKM Matrix In SM weak charged transitions mix quarks of different generations Encoded in unitary CKM matrix Unitarity  4 independent parameters, one of which is the complex phase and sole source of CP violation in SM Wolfenstein parameterisation: quark transition J.Michael Roney

38. CKM Unitarity Triangle Physics beyond the SM signaled by breakdown of unitarity of CKM matrix Wolfenstein parameterisation defined to hold to all orders in l~0.2 and rephasing invariant Area of Δ~CP violation J.Michael Roney

39. CKM experimental programme • Make as many precision measurements as possible that overconstrain the four CKM parameters (A, λ, ρ,η) • New Physics would be revealed in discrepancies between measurements • Generally requires non-perturbative QCD input to convert measurements to a SM CKM interpretation J.Michael Roney

40. Programme: Over constrain CKM with broad set of measurements Quantity Sample Measurement(s) Although we probe the charged weak interaction, we need input from strong interaction calculations, which are difficult and often need data J.Michael Roney

41. Graphically present results as overconstrainedUnitarity Triangle levels@ 95%Prob CKM Fitter group uses frequentist framework UTFit uses Bayesian framework J.Michael Roney

42. Select Two interesting non-CP violating measurements • B leptonic decays • |Vus| measurements J.Michael Roney

43. Leptonic Decays Remarkably simple pseudo-scalar (spin = 0, Parity is negative) decays carry information about CKM elements, but come with a 'decay constant' factor which accounts for the strong interaction component • B→τν rate of decay α (fB|Vub|)2 • Ds→τν or Ds→μν rate α (fDs|Vcs|)2 • K→μν rate α (fK|Vus|)2 J.Michael Roney

44. l+ b + W+ B+ u nℓ l+ b H+ B+ u nℓ Leptonic decays Particularly interesting because some New Physics theories have charged Higgs which contributed to the observed decay rate, e.g. • Additional tree level contribution from a charged Higgs • It does not suffer from helicity suppression, but gets the same ml dependence from Yukawa coupling • Branching fraction theoretical expression depends on the NP model W. S. Hou, Phys. Rev. D 48 (1993) 2342. A.G. Akeroyd and S.Recksiegel J.Phys.G29:2311-2317,2003 J.Michael Roney

45. B+→τ+ντ Experimental method e+,μ+ X- Fully reconstructthis side: ‘tag’ Then look for signal this side: ‘signal’ νμ,νe ϒ(4S) τ+ B- B+ Two approaches to reconstruct the ‘tag’, which are classified as hadronic or semileptonic • select signal candidate and check that remaining particles consistent with B decay (inclusive Btagreco) • Reconstruct Btag in exclusive modes and check if remaining particles consistent with Bsignal ντ ντ D(*)0 In reality at the ϒ(4S) the B+ and B- decay products all overlap J.Michael Roney

46. Reconstruct event to select B-events from background… J.Michael Roney

47. ....and look for excess of missing energy associated with the neutrino J.Michael Roney

48. B+→τ+ντ Results BABAR Hadronic Phys. Rev. D 77, 011107(R) (2008) BABAR Semi-leptonic Phys. Rev. D 81,051101(R) (2010) BELLE Hadronic Phys. Rev. Lett. 97, 261802 (2006) BELLE Semi-leptonic arXiv:1006.4201[hep-ex] J.Michael Roney

49. B+→τ+ντ Results New BaBar preliminary result: see ICHEP 2010 deNardo talk

50. B+→τ+ντ Results world average pre-ICHEP 2010: B(B+→τ+ν)=(1.73±0.35)x10-4 ~2.5σ higher than expected from CKM fit excluding B+→τ+ν J.Michael Roney