1 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond Palm tree and CKM Beauty in the Standard Model and Beyond Gabriella Sciolla (MIT) CIPANP Puerto Rico - May 30 - June 3, 2006

2 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond Palm tree and CKM Beauty in the Standard Model and Beyond Gabriella Sciolla (MIT) CIPANP Puerto Rico - May 30 - June 3, 2006

3 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond Outline The beauty of B physics CP violation in the B system and the Unitarity Triangle Standard Model measurements Sensitivity to New Physics Measurements of CP violation in B decays The experiments Measurement of the angles and sides of the Unitarity Triangle What have we learned? Summary and conclusion

4 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond CP violation What is CP? Why is CP violation interesting? Crucial ingredient to explain the matter-dominated universe A. Sakharov (1967) CP violation is expected in the Standard Model Until recently, one of the least tested aspect of the theory Many new sources of CP violation Beyond the Standard Model Sensitive to New Physics C: Charge Conjugation Particle  Anti-particle P: Parity Inverts space coordinates CP = C × P

5 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond CP violation in the Standard Model Discovered by Fitch and Cronin in 1964 in K L decays Introduced in Standard Model in 1973 by Kobayashi and Maskawa In KM mechanism, CP violation originates from a complex phase in the quark mixing matrix (CKM matrix) b c W-W- A, (Cabibbo angle): very well measured  : poorly known until recently First goal of CP violation studies: Precise determination of the parameters  and 

6 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond Pros and Cons of CKM Pros: Elegant and simple explanation of CPV in SM It is very predictive: only one CPV phase It accommodates all experimental results Indirect CP violation in K   and K L   l Direct CP violation in K   CP violation in the B system Cons:  n B /n  predicted by CKM « observed value …by orders of magnitude!  New sources of CPV must exist besides CKM!. CP violation as a probe for New Physics: Measure CP violation in channels theoretically well understood and look for deviations w.r.t. SM expectations

7 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond Unitarity of CKM implies: V † V = 1  6 unitarity conditions Of particular interest: All sides are ~ O(1)  possible to measure both sides and angles! CP asymmetries in B meson decays measure  and  Sides from semileptonic B decays, B mixing, rare B decays The Unitarity Triangle     

8 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond Standard Model or New Physics?       Two ways of looking for New Physics: Compare measurement of sides and angles 2 measurements define the apex; >2 test Standard Model All pieces of the puzzle must fit: inconsistencies mean New Physics Measure same quantity in channels with different sensitivity to NP E.g.: measure  in modes mediated by different decay diagrams Precision and redundancy are essential!

9 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond The experiments: B factories BaBar (SLAC) and Belle (KEK) e + e - asymmetric collisions.   (4S) resonance Advantages of the B factories No need for bb trigger Very clean environment: High luminosity Peak luminosity > cm -2 s -1 Integrated luminosity 350/600 fb -1 (BaBar/Belle)

10 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond The experiments: Tevatron experiments CDF and D0 at Fermilab. Challenges of the Tevatran Special trigger necessary for B events High multiplicity events Advantages of the Tevatron Large number of B produced L~10 32 cm -2 s -1 but high x-sections Integrated luminosity: >1 fb -1 All b hadrons are produced B S,  b, B C,… Complementary to B factories

11 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond The measurements    The angle  

12 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond B  f CP exclusive reconstruction How to measure the CP asymmetry. e-e- Flavor tagging Q=(30.5  0.5)%  (4S) B0B0 B0B0 e-e- ++ -- e+e+ ++ -- Precise  t determination  z~  c  t

13 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond CP violation at the B factories mixing decay (f)(f) When only one diagram contributes to the final state, | |=1 A CP (t) = ± Im sin(  mt) (CP violation in interference between mixing and decays in B 0 )

14 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond CP violation in B 0 decays: sin2  For some modes, Im is directly and simply related to the angles of the Unitarity Triangle. Example: B 0  J/  K S : the “golden mode” Theoretically clean Experimentally clean Relatively large BF (~10 -4 )      A CP (t) = sin2  sin  mt

15 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond The golden mode for sin2  : sin2  in B 0  J/  K S Belle 386 fb -1 m ES [GeV/c 2 ] sin(2  ) = ± WA EPS 2005 Belle 386 fb -1 B 0  J/  K S      Belle 386 fb -1  t [ps] sin(2  )= ± ± 0.020

16 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond Unitarity Triangle constraints sin2  vs indirect UT constraints: very good agreement! New Physics does not show up in the golden mode  SM reference Compare with sin2  in independent modes with different sensitivity to NP CKM mechanism is the dominant source of CPV at low energies 95% CL from sides  

17 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond The key to New Physics: The Penguin Modes Decays dominated by gluonic penguin diagrams The typical example: B 0   K S No tree level contributions: theoretically clean SM predicts: A CP (t) = sin2  sin(  mt) Impact of New Physics could be significant New particles could participate in the loop  new CPV phases Low branching fractions (10 -5 ) Measure A CP in as many b  sqq penguins as possible! φ K 0, K + K − K S, η′ K S, K S π 0, K S K S K S, ω K S, f 0 (980) K S SM NP

18 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond The golden penguin: B 0   K 0 N(  K s )=180 ± 16 Belle 386 fb -1 B0KSB0KS B0KLB0KL

19 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond The silver penguin: B 0   ’K S Larger BF ~ 6 x but theoretically slightly less clean than  K S S η′K s = 0.30 ± 0.14 ± 0.02 C η′K s = −0.21 ± 0.10 ± 0.02 BaBar 210 fb -1

20 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond “sin2  ” in penguins  A trend is visible  although each measurement is compatible with J/  K S …  Most significant shift in  ’K S  ~2.1   Naïve average: 0.50±0.06  ~2.5  … statistical errors still large… BaBar + Belle average Penguin modes Golden mode J/  K S

21 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond The measurements    The angle  

22 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond sin2  in        Tree diagram dominates Relatively large Branching Fraction B (B 0 →       ) = (25.2 ± 3.7 )×10  6 Penguin contribution small B (B 0 →       ) < 1.1×10  6 (90%C.L.) Vector-vector final state: is CP defined? In principle admixture of CP+ and CP- eigentastes… A CP (t) = sin2  sin  mt Penguin Tree

23 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond Is CP defined in        ? Vector-vector final state 3 possible L states Measure fraction of longitudinal polarization in angular analysis BaBar 210 fb -1 ~ 100% longitudinally polarized  CP even eigenstate

24 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond CP asymmetry in B 0 →     BaBar 210 fb -1

25 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond Combined constraints on  Average of BaBar and Bellecfr: CKM fit 

26 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond The measurements    The angle  

27 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond The angle . Cabibbo allowedCabibbo and color suppressed NB: only tree diagrams: 100% Standard Model

28 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond  from B → DK GWL (Gronau, Wyler, London) D  CP eigenstate Theoretically clean Small interference: needs more data ADS (Atwood, Dunietz, Soni) is doubly Cabibbo suppressed Larger interference Needs more data Dalitz method (Giri, Grossman, Soffer, Zupan) Exploits interference pattern in Dalitz plot in D  K S     Combines many modes  statistical advantage Small systematics due to Dalitz model Currently most sensitive D0KS+-D0KS+- See talk by M. Verderi

29 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond Summary of  measurements Direct measurement on  BaBar + Belle, all methods combined Indirect constraints: UTFit

30 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond The left side: R b    NB:  is the best measured quantity in the Unitarity Triangle  precise measurement of R b is needed for accurate tests of SM

31 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond Semileptonic B Decays Sensitive to hadronic effects Theory error not negligible Prob(b  c)/Prob(b  u)~50 V cb precisely measured (  2%) V ub is the challenge Parton level l Hadron level l

32 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond Two approaches to V ub Inclusive B  X u l Hadronic final state is not specified b  c l background is suppressed using kinematical variables Partial rate is measured  theoretical uncertainties ~5% Inclusive B  X u l Exclusive B   l Better S/B but lower branching fraction (10 -4 ) Needs form factor calculation from Lattice QCD  uncertainty of ~ 12% l-l- ll-l-

33 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond |V ub | from Inclusive B  X u l Close collaboration between theorists and experimentalists led to c.f.r.: precision on  :  5.5% World Average 4.45  0.33  2 /dof = 5.5/6 Precision on V ub :  7.4%

34 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond The last side of the triangle: R t   

35 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond The measurement of R t B s /B d oscillations Theory error <5%  m d is precisely measured But B s mixing is very hard…   

36 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond History of B S mixing 6 experiments, > 10 years of work Then early this Spring… D0: double sided limit on  m S CDF: first observation of B S mixing Dec 2005

37 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond B S mixing at the Tevatron. Reconstruction of B S decay in hadronic or SL modes Flavor tagging Q SST ~4% Q OST ~1% Time reconstruction  (ct)~26-70  m Talk on Fri by Matthew Jones

38 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond D0 result. B s  μD s : 5601±102  m s < 21 ps 90% CL assuming Gaussian errors Most probable value of  m s = 19 ps -1

39 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond CDF result Probability of random fluctuation: ~0.5% 3,700 events

40 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond Impact of  m S on Unitarity Triangle

41 G. Sciolla – M.I.T. Beauty in the Standard Model and Beyond Conclusion Standard Model: precision Tremendous improvement in  and  Precision ~ 0.05 First quantitative test of CPV in SM CKM is the dominant source of CPV New Physics: redundancy Sides vs angles in agreement with SM First signs of NP in sin2  in penguins? More statistics will help: Analyzed: ~500 fb -1 Available: ~1 ab -1 By 2008: > 2 ab -1. BaBar+Belle CP-violating measurements CP-conserving measurements