Flavor physics. Yuval Grossman. Cornell. Y. Grossman Flavor physics APS2009, Denver, 5/2/2009 p. 1

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1 Flavor physics Yuval Grossman Cornell Y. Grossman Flavor physics APS2009, Denver, 5/2/2009 p. 1

2 Flavor at a junction Every end is a new beginning End: The Nobel to KM is a formal declaration that the CKM picture of flavor is correct Beginning: Looking for corrections to the SM picture of flavor Y. Grossman Flavor physics APS2009, Denver, 5/2/2009 p. 2

3 Outline The new physics flavor problem Current status of the SM flavor sector The highlight of recent results: D D mixing The new goal of flavor physics: going beyond the SM Y. Grossman Flavor physics APS2009, Denver, 5/2/2009 p. 3

4 The new physics flavor problem Y. Grossman Flavor physics APS2009, Denver, 5/2/2009 p. 4

5 The SM is not perfect... We know the SM does not describe gravity At what scale it breaks down? We parametrize the NP scale as the denominator of an effective higher dimension operator. The weak scale is roughly L eff = µeν ν Λ 2 Λ W 100 GeV W The effective scale is roughly the masses of the new fields times unknown couplings Flavor bounds give Λ 10 4 TeV Y. Grossman Flavor physics APS2009, Denver, 5/2/2009 p. 5

6 The flavor bounds Q: Why the flavor bounds are so tight, Λ 10 4 TeV? A: Because in the SM there are many suppression factors (and the data agree with the SM) m 2 c m 2 W 1 16π 2 α2 W V 2 us arg(v us ) The naive scale of the operator that generate ǫ K is Λ 10 4 TeV In the SM there is a suppression of 10 10, so the mass scale is five order of magnitudes smaller, 100 GeV Y. Grossman Flavor physics APS2009, Denver, 5/2/2009 p. 6

7 Flavor and the hierarchy problem There is tension: The hierarchy problem Λ 1 TeV Flavor bounds Λ 10 4 TeV Any TeV scale NP has to deal with the flavor bounds Such NP cannot have a generic flavor structure Flavor is mainly an input to model building, not an output Y. Grossman Flavor physics APS2009, Denver, 5/2/2009 p. 7

8 Dealing with flavor Any viable NP model has to deal with this tension. Thus, the NP at the TeV must not be generic At what level we expect to see deviations from the SM predictions? There is no simple answer. Naively, we should have seen it already One class of models can accommodate large flavor violations. That is, as large as current bounds The other is Minimal Flavor Violation (MFV): The NP at the TeV has minimal impact on flavor Roughly, even in MFV we expect O(1%) effects. Clearly the exact numbers and modes are important Y. Grossman Flavor physics APS2009, Denver, 5/2/2009 p. 8

9 The goal of flavor physics Flavor physics must look for problems with the SM in order to see the nature of the NP Past : Confirmation that the SM explain flavor physics at leading order Future : Looking for small deviations from the SM predictions. As a rough guideline aiming at the 1% level The main issue is theoretical uncertainties, that is, QCD. The name of the game is to try to overcome QCD and get to the fundamental physics Y. Grossman Flavor physics APS2009, Denver, 5/2/2009 p. 9

10 Current status of the SM flavor sector Y. Grossman Flavor physics APS2009, Denver, 5/2/2009 p. 10

11 The SM flavor sector At present there are no significant deviations from the SM predictions in the flavor sector Even the hints we had in the last few years are now weaker Global fit a CP (B ψk S ) vs a CP (B φk S ) B Kπ Polarization in B V V Y. Grossman Flavor physics APS2009, Denver, 5/2/2009 p. 11

12 Current status of the global fit excluded area has CL > 0.95 γ excluded at CL > 0.95 m d & m s sin 2β 0.5 m d ε K α η α V ub SL V ub τ ν γ β α 1.0 CKM f i t t e r Moriond 09 γ ε K sol. w/ cos 2β < 0 (excl. at CL > 0.95) ρ Y. Grossman Flavor physics APS2009, Denver, 5/2/2009 p. 12

13 Global fit: closer look η excluded area has CL > 0.95 γ sin 2β ε K m d α m d & m s ε K CKM f i t t e r Moriond 09 sol. w/ cos 2β < 0 (excl. at CL > 0.95) α 0.1 α V ub γ β Very impressive agreement One small problem: The rate of B τν ρ Y. Grossman Flavor physics APS2009, Denver, 5/2/2009 p. 13

14 CP asymmetries in b s ss modes Time dependent CP asymmetries measure the phase between the mixing and twice the decay amplitudes In the SM arg(a mix ) = 2β arg(a b c cs ) = 0 (Tree) B ψk S arg(a b s ss ) = 0 (Penguin) B φk S, B η K S... To first approximation the SM predicts a CP (B ψk S ) = a CP (B φk S ) = sin 2β The theoretical uncertainties are small, roughly, O(5%) Y. Grossman Flavor physics APS2009, Denver, 5/2/2009 p. 14

15 b sss data b ccs K + K - K 0 π 0 π 0 K π 0 K 0 η K 0 S ω K S φ π 0 K f ρ 0 K K φ K 0 S 0 K S S S K S K S sin(2β eff ) sin(2φ e 1ff ) HFAG CKM2008 CKM2008 HFAG World Average 0.67 ± 0.02 BaBar 0.26 ± 0.26 ± 0.03 Belle Average BaBar 0.57 ± 0.08 ± 0.02 Belle 0.64 ± 0.10 ± 0.04 Average 0.59 ± 0.07 BaBar Belle 0.30 ± 0.32 ± 0.08 Average 0.74 ± 0.17 BaBar 0.55 ± 0.20 ± 0.03 Belle 0.67 ± 0.31 ± 0.08 Average 0.57 ± 0.17 BaBar ± 0.09 ± 0.08 Belle ± 0.09 ± 0.10 Average BaBar ± 0.02 Belle 0.11 ± 0.46 ± 0.07 Average 0.45 ± 0.24 BaBar Belle Average BaBar ± 0.71 ± 0.08 Belle ± 0.49 ± 0.09 Average ± 0.41 BaBar Average BaBar 0.86 ± 0.08 ± 0.03 Belle 0.68 ± 0.15 ± Average 0.82 ± 0.07 HFAG HFAG HFAG HFAG CKM2008 HFAG HFAG CKM2008 CKM2008 CKM2008 HFAG CKM2008 CKM2008 CKM2008 HFAG HFAG CKM2008 CKM2008 H F A G H F A G CKM2008 PRELIMINARY Combine (< 1σ) S P = 0.64 ± 0.04 S T = 0.67 ± Y. Grossman Flavor physics APS2009, Denver, 5/2/2009 p. 15

16 B Kπ Consider the four decays B + K 0 π + b d ds B + K + π 0 b d ds or b uūs B 0 K + π b uūs B 0 K 0 π 0 b d ds or b uūs There are many SM relations between these modes To first approximation, all the rates are equal since the penguin diagram dominate The data used to be problematic, but not any more One problem is A K+ π 0 A K + π = 0.15 ± 0.03 Y. Grossman Flavor physics APS2009, Denver, 5/2/2009 p. 16

17 The status of the SM flavor sector Overall, the SM is very successful in describing flavor At present there are no real hints for NP at the flavor sector We did not really expect deviation at that level. Need to go to the next level Eventually, theory will be the limiting factor (not there yet) Y. Grossman Flavor physics APS2009, Denver, 5/2/2009 p. 17

18 New flavor results: D D mixing Y. Grossman Flavor physics APS2009, Denver, 5/2/2009 p. 18

19 D D mixing Not easy since the mixing is very small x m Γ y Γ 2Γ First observation of the mixing It was found by combining several decay modes D K + K D π + π D Kππ D Kπ More than 5σ signal for oscillation in the combined fit x y 1% No signal for CPV Y. Grossman Flavor physics APS2009, Denver, 5/2/2009 p. 19

20 D D mixing: data Y. Grossman Flavor physics APS2009, Denver, 5/2/2009 p. 20

21 D D mixing: Theory Two parameters x m Γ y Γ 2Γ Can we calculate them in the SM? Very hard to calculate. The charm is not really heavy and not really light The only robust SM prediction is that there is no CPV Y. Grossman Flavor physics APS2009, Denver, 5/2/2009 p. 21

22 D D mixing predictions Mixing Amplitude ( x, y, etc.) D 0 -D 0 Mixing Predictions Mixing Rate (1/2 Amplitude ) H. Nelson,hep-ex/ : NP predictions for x : SM predictions for x : SM predictions for y Reference Index Y. Grossman Flavor physics APS2009, Denver, 5/2/2009 p. 22

23 SU(3) breaking The contribution form the third generation is negligible D D mixing vanishes in the flavor SU(3) limit (GIM mechanism) It arises only at second order in SU(3) breaking x,y sin 2 θ C ε 2 SU(3) ε SU(3) m s Λ What is Λ? Λ m c x,y 10 3 Λ Q m c x,y 10 2 The larger value is preferred Y. Grossman Flavor physics APS2009, Denver, 5/2/2009 p. 23

24 Still, we can learn a lot Any signal of CPV is a signal on NP Already now, the combination of K and D bounds put significant bounds on NP models. TeV scale NP must have some amount of universality The pattern of CPV can teach us about the NP. For example, if the NP is only significant in the mixing we have ya CP (D Kπ) = xa SL Y. Grossman Flavor physics APS2009, Denver, 5/2/2009 p. 24

25 The future of flavor physics Y. Grossman Flavor physics APS2009, Denver, 5/2/2009 p. 25

26 What next for flavor physics? We need to aim at the 1% level to find deviations from the SM Can we go below the 1% level? Experimentally. Yes (but I am not going to talk about it) Theoretically. Yes! B DK B s ψφ CPV in D decays K L π 0 ν ν... Y. Grossman Flavor physics APS2009, Denver, 5/2/2009 p. 26

27 Conclusions Y. Grossman Flavor physics APS2009, Denver, 5/2/2009 p. 27

28 Conclusions It is not easy to understand why the SM describes flavor so well A very rough prediction is that we will see deviation at or above the 1% level There are few modes that give superb theoretical predictions, and we can go and probe flavor below the 1% level Y. Grossman Flavor physics APS2009, Denver, 5/2/2009 p. 28