Flavor Physics at Belle and Belle II Peter Kri an University of - PowerPoint PPT Presentation

Flavorful Ways to New Physics Waldhotel Zollernblick, Oct 28-31, 2014 Flavor Physics at Belle and Belle II Peter Kri ž an University of Ljubljana and J. Stefan Institute “Jožef Stefan” University Institute of Ljubljana Peter Križan, Ljubljana

Contents  Introduction with a little bit of B factory primer  B factories: recent results  Super B factory: status and outlook  Summary Peter Križan, Ljubljana

Flavour physics at the luminosity frontier with asymmetric B factories KEKB √s=10.58 GeV e + e - B D z ~ c bgt B Υ (4s) (4s) Υ (4s) (4s) 00 m m B ~ 200 (e - )=9 GeV (e + )=3.1 GeV eV bg =0. BaBa aBar p(e eV p(e =0.56 (e - )=8 GeV (e + )=3.5 GeV eV bg =0 Bel elle p(e eV p(e =0.42 To a large degree shaped flavour physics in the previous decade Peter Križan, Ljubljana

Advantages of B factories in the LHC era Unique capabilities of B factories:  Exactly two B mesons produced (at U (4S))  High flavour tagging efficiency  Detection of gammas, p 0 s, K L s  Very clean detector environment (can observe decays with several neutrinos in the final state!)  Well understood apparatus, with known systematics, checked on control channels Peter Križan, Ljubljana

Integrated luminosity at B factories Fantastic performance far beyond design values! In addition to  (4S) also large samples of other  (nS) decays! # of produced  (nS) Peter Križan, Ljubljana

CP violation in the B system and unitarity triangle B 0  p - p + ,  +  - h V ud ud V ub * ub * V td td V tb * V cd cd V cb tb cb V cd cd V cb * f 2 (a) cb B 0  J/ Ψ K 0 f 3 (g) B  D K f 1 (b)  (0,1) (0,1) (0,0) (0,0) Peter Križan, Ljubljana

B factories: CP violation in the B system CP violation in the B system: from the discovery (2001) to a precision measurement (2011). Peter Križan, Ljubljana

Comparison of energy / intensity frontiers To observe a large ship far away one can either use strong binoculars or observe carefully the direction and the speed of waves produced by the vessel. Energy frontier (LHC) Luminosity frontier - (super) B factories Peter Križan, Ljubljana

The unitarity triangle – new/final measurements Constraints from measurements of angles and sides of the unitarity triangle  Remarkable agreement, but still 10-20% NP allowed Selected results:  sin2 f 1 (=sin2 b ): final measurements  f 2 (= a ): final measurements  f 3 (= g ): new model-independ. method  Rare decays Peter Križan, Ljubljana

CP violation measurement Want to measure the asymmetry between B and anti-B mesons, ( ) 0 -    f D 0 t  P ( B ( B ) f , t ) e 1 sin( 2 ) sin( mt ) CP 1  Want to distinguish the decay rate of B (dotted) from the decay rate of anti-B (full). Integrals are equal, time information mandatory! (true at Y(4s), but not for incoherent production) Resolution ~B lifetime Peter Križan, Ljubljana

B meson production at Y(4s) Peter Križan, Ljubljana

CP violation measurement Measure the difference in time evolution in B 0 Measure the difference in time evolution in anti-B 0 decays to a and anti and decays to a CP eigenstate CP eigenstate m + Fully reconstruct decay Fully reconstruct decay m - B 0 or B or B 0 J/ y J/ to CP eigenstate to CP eigenstate p - B CP (4s) CP Tag flavor Tag flavor Υ (4s) p + K s l - of other B of other B K - from from B tag tag D t= t= D z/ z/ bg c charges charges determined determined of typical of typical B 0 (B (B 0 ) decay decay Determine time between decays Determine time between decays products products CMS should be boosted! CMS should be boosted! Peter Križan, Ljubljana

Experimental considerations Detector form: symmetric for symmetric energy beams; slightly extended in the boost direction for an asymmetric collider. cms lab Exaggerated p* plot: in reality bg =0.5 bg p* CLEO BELLE Peter Križan, Ljubljana June 5-8, 2006

Belle spectrometer at KEK-B m and K L detection system Aerogel Cherenkov Counter (14/15 layers RPC+Fe) (n=1.015-1.030) 3.5 GeV e + Silicon Vertex Detector (4 layers DSSD) Electromag. Cal. (CsI crystals, 16X 0 ) 8 GeV e - Central Drift Chamber (small cells, He/C 2 H 6 ) ToF counter 1.5T SC solenoid Peter Križan, Ljubljana

Reconstruction of rare B meson decays Reconstructing rare B meson decays at Y(4s): use two variables, beam constrained mass M bc and energy diference DE  D  - E E E 2 i CM    - 2 2 M ( E / 2 ) ( p ) bc CM i Peter Križan, Ljubljana

Continuum suppression qq Continuum continuum e - e Jet-like + Y (4S) - BB Other B e + e - → qq “continuum” (~3x BB) e e - + BB To suppress: use event shape variables spherical Signal B Peter Križan, Ljubljana

CP violation measurement Want to measure the asymmetry between B and anti-B mesons, ( ) 0 -    f D 0 t  P ( B ( B ) f , t ) e 1 sin( 2 ) sin( mt ) CP 1  Want to distinguish the decay rate of B (dotted) from the decay rate of anti-B (full). Integrals are equal, time information mandatory! (true at Y(4s), but not for incoherent production) Resolution ~B lifetime Peter Križan, Ljubljana

Final measurement of b sin2 f 1 (=sin2 b ) f 1 from CP violation measurements in B 0 → cc K 0 Final measurement: with improved tracking, more data, improved cc K S cc K L systematics (50% more statistics than last result with 492 fb -1 ); cc = J/ y , y (2S), c c1  25k events Detector effects: wrong tagging, finite D t resolution  determined using control data samples cc K L cc K S Belle, final, 710 fb -1 , PRL 108, 171802 (2012) Peter Križan, Ljubljana

K L detection Important cross check: Measure CP violation for B  CP=+1 eigenstate  B  J/ y K L Need a detector for K L s – muon detections system acts as a hadron calorimeter Measure only the K L interaction point coordinate, not the K L energy. Peter Križan, Ljubljana

Final measurements of b sin2 f 1 (=sin2 b ) f 1 from B 0 → cc K 0 Final results for sin2 f 1 Belle, PRL 108, 171802 (2012) Belle: 0.668 ± 0.023 ± 0.012 BaBar, PRD 79, 072009 (2009) BaBar: 0.687 ± 0.028 ± 0.012 with a single experiment precision of ~4%! Comparison with LHCb: • The power of tagging at B factories: 33% vs ~2-3% at LHCb • LHCb: with 8k tagged B d → J/ψK S events from 1/fb measured sin2β = 0.73 ± 0.07(stat.) ± 0.04(syst.) • Uncertainties at B factories - e.g., Belle final result sin2β = 0.668 ± 0.023(stat.) ± 0.012(syst.) - are 3x smaller than at LHCb Peter Križan, Ljubljana

Final measurement of f 2 ( a ) in B → p + p - decays a f 2 from CP violation measurements in B 0 → p + p - Belle, 710 fb -1 PRD 88 , 092003 (2013)  a f CP  D + D C cos( mt ) S sin( mt ) Belle, this measurement: BaBar: S = − 0.64 ± 0.08 ± 0.03 S = −0.68 ± 0.10 ± 0.03 C = − 0.33 ± 0.06 ± 0.03 C = −0.25 ± 0.08 ± 0.02 Peter Križan, Ljubljana

Measurement of B → p 0 p 0 decays f 2 from CP violation measurements in B 0 → p + p - Extraction not easy because of the penguin contribution. BR for the B → p 0 p 0 decay important to resolve this issue. Pit Vanhoefer, CKM2014 Hard channel to measure: four gammas, continuum (ee  qq) background Theory: BR<1x10-6 (Phys.Rev.D83:034023,2011) • Belle, 1/3 of data PRL 94, 181803(2005) = (2.32 +0.4-0.5 +0.2-0.3) 10 -6 • BaBar PR D87 052009 (1.83 ± 0.21 ± 0.13 ) 10 -6 • Belle new result with full data set: Improved rejection of out-of-time electromagnetic calorimeter hits (some of which contribute to a peaking background). Peter Križan, Ljubljana

Measurement of B → p 0 p 0 decays a Preliminary Br( B  p 0 p 0 ) = (0.90 ± 0.20 (stat) ± 0.15(syst) )∙10 -6 (6.7 s significance) A CP under preparation  stay tuned Peter Križan, Ljubljana

Improved measurement of f 2 ( a ) in B → pp, , p decays a f 2 ( a ) from CP violation and branching fraction measurements in B → pp, , p f 2 = a = ( 85.4 +4.0 − 3.8 ) degrees http://ckmfitter.in2p3.fr/www/results /plots_fpcp13/ckm_res_fpcp13.html Still to be updated for the final version: new results expected from Belle on  +  - , p; a new p, analysis published by BaBar  PRD88, 012003 (2013) . Peter Križan, Ljubljana

f 3 (= g ) with Dalitz analysis A. Giri et al., PRD68, 054018 (2003) GGSZ method: A. Bondar et al (Belle), Proc. BINP Meeting on Dalitz Analyses, 2002 The best way to measure f 3 ( ) D 0 → K S p + p - g 3-body D 0 → K S p + p - Dalitz amplitude Model dependent description of f D using continuum D* data  systematic uncertainty f 3 =(78 ± 12 ± 4 ± 9) o f 3 =(68 ± 14 ± 4 ± 3) o Peter Križan, Ljubljana Belle, PRD81, 112002, (2010), 605 fb -1 BaBar, PRL 105, 121801, (2010)