The physics of b s l + l - : 2004 and beyond Jeffrey Berryhill University of California, Santa Barbara January 19, 2004 Super B Factory Workshop University of Hawaii

Electroweak Penguin Decays and New Physics B decays in the SM via electroweak loop diagrams Many observables accurately predicted with sensitivity to new physics at the electroweak scale (SUSY, e.g.): CP asymmetries, rates, angular distributions More complex interaction than b to s  rates and distributions depend on the magnitude and relative phase of three separate diagrams

b s l + l - and Effective Field Theory Matrix elements computed from effective Hamiltonian for b to s transitions Products of field operators Wilson coefficients encoding short-distance physics 3 of the 10 b to s operator products give b to s l+l -: C7: photon penguin (|C7| measured from b to s  ) C9,C10 : Z penguin and W box C9,C10 dominant at high s, C7 dominant at low s, sign of C7 matters Generally decreases with s

LO: more missing states, lower lepton momenta C7*C9 dominant HI: fewer missing states, higher lepton momenta C10 dominant Dilepton Mass Spectrum d  /ds NNLO error = 19% NNLO error = 12%

HI: check for right sign and magnitude LO: extract s 0 Angular Asymmetry vs. Dilepton Mass Forward-backward asymmetry of lepton pair in the B rest frame S 0 NNLO error = 5% S 0 = / ~ C7/C9 NNLO error = 5%

CP Asymmetries Like b to s , in the SM ACP in b to s l+ l- is small, < 1% In B to K* l+l-, can construct 8 different angular and CP asymmetries, all of which are << 1% in the SM (Kruger et al., hep-ph/ ) In units of ! CP asymmetry in AFB(s) for s> m(  (2S)) 2 gives access to Im(C10) (Buchalla,Hiller,Isidori, hep-ph/ )

Isospin Asymmetry vs. Dilepton Mass Asymmetry arising from non-factorizable diagrams Sensitive to b to s 4-quark operators Feldmann and Matias hep-ph/ C5,C6 dominant C3,C4 dominant Independent test of sign of C7!

SUSY Higgs Physics at a B-Factory In SUSY with large tan , Higgs penguins introduce new scalar and pseudoscalar operators to the b to s H eff, with new Wilson coefficients Cs, Cp b to s e+ e- is unaffected b to s  +  - is enhanced (by larger Yukawa coupling) Ratio of exclusive rates is very precisely predicted in SM: R K = BF(B to K  +  -)/BF(B to K e+ e-) = 1 +/ ! (Hiller and Kruger, hep-ph/ ) R K is a powerful probe of SUSY Higgs with large tan  Complementary observable to the decay rate for B s to  +  -

K l + l - Includes K and Ks final states 2-D ML fit to (m ES,  E) data Background shape and normalization float in the fit Dilepton mass consistent with signal BF = ( /-0.4)x10 -7 Smallest B BF Ever Measured!

K*l+l-K*l+l- Includes K* final states: K*0 to K+ pi- K*+ to Ks pi+ 3-D fit to (m ES,  E, m K  ) data Dilepton mass consistent with signal (all the way down to q 2 = 0) BB background is larger than in Kll. BF = /-1.0 X 10 -7

s l + l - Sum of exclusive final states: 1 K or Ks + <= 2 pions (pi0, pi+, pi0pi+, pi+pi-) M(Xs) < 1.8 GeV P(e) > 0.5 GeV, P(mu) > 1.0 GeV 1-D fit to m ES data >= 3 pion states added negligible significance K, K* and higher mass states contribute to observed signal Model-dependence of efficiency Is the dominant systematic BF = 6.3+/-1.6+/-1.8 X 10 -6

b sl + l - January 2004 Branching fractions in good agreement with SM predictions Experimental precision of overall rates already comparable to theoretical precision!

“Model Independent” Analysis of H eff C7 < 0 C7 > 0 C10 C9 Attempt to extract Wilson coefficients C9, C10 directly from total b to s l+ l- BF (|C7| fixed from b to s  Adding more observables will further constrain C9 and C10 Can real and imaginary parts of all coefficients be extracted via a combined fit to all observables (a la b to c l )?

Projected Statistical Uncertainty: K l + l - 2 ab ab ab K l + l - All s 5.4%2.4%1.1% K l + l - Low s 6.9%3.1%1.4% K l + l - High s 11.5%5.1%2.3% Based on HFAG average stat. errors, relative efficiency vs. s of BaBar RED = detector systematics limited for absolute rate

Projected Statistical Uncertainty: K* l + l - 2 ab ab ab K* l + l - All s 7.0%3.1%1.4% K* l + l - Low s 9.9%4.4%2.0% K* l + l - High s 13.8%6.2%2.8% Based on HFAG average stat. errors, relative efficiency vs. s of BaBar RED = detector systematics limited for absolute rate

Projected Statistical Uncertainty: s l + l - 2 ab ab ab s l + l - All s 4.5%2.0%0.9% s l + l - Low s 7.5%3.4%1.5% s l + l - High s 11.4%5.1%2.3% Based on HFAG average stat. errors, relative efficiency vs. s of BaBar RED = detector systematics limited for absolute rate BLUE = probably theory systematics limited for absolute rate

Physics prospects beyond The BAD NEWS: Absolute rates and even partial absolute rates will be systematics limited in the B- factory (10 34 ) era The GOOD NEWS: Relative rates and asymmetries will be statistics limited for both and 10 36

K* l+l- should have comparable sensitivity to AFB as s l+ l- Precision in s0 ~ 5%.

Model Independent Analysis beyond Fit directly for C9 and C10 using the AFB spectrum (Nakao study for SuperBelle) C7 is fixed from future precise b to s  BF

Detector design considerations Need efficient lepton ID down to the lowest lab momentum possible (1 GeV cut on muons cuts into efficiency at low s) Lepton fake rate not the highest priority (peaking backgrounds are low) Better vertex separation will improve background rejection Worse separation will not seriously degrade sensitivity

The Competition 1-2 years of design luminosity with hadrons = 50 ab -1 with electrons!! 1/sqrt(4400)=1.5% = SuperB precision

Physics prospects beyond With Competition The BAD NEWS: One or more successful hadron experiments can do better with most measurements than e+e- experiments, even with 50 ab -1. Possible Exceptions: R K : precise Kee is difficult with hadron experiments. sll observables : probably done better at e+e- (though not uniquely), but do they tell us something exclusive modes will not?

Conclusions The b s l+ l- system has a rich set of observables sensitive to new physics at the electroweak scale In the SuperB era, absolute rate measurements will be systematics limited, but many relative rates and asymmetries with high sensitivity to new physics will be statistics limited: Forward-backward asymmetry vs. dilepton mass CP and isospin asymmetries Most of these measurements can be done (in theory, done better) by hadron experiments Ratio of rates R K = BF( K  )/BF( Kee ) is a measurement unique to a SuperB Factory with access to Higgs physics in SUSY models with large tan 

Combinatorial Background: Reduction and Estimation Background from random track combinations in BB or continuum events Continuum events reduced with Fisher discriminant: Fox-Wolfram moments B angle with CM z axis B angle with thrust axis K l mass BB events reduced with likelihood function: missing energy B vertex probabilities B angle with CM z axis Separate background from signal with multivariate discriminants Signal efficiency verified with J/  K (*) events Background reduction verified with: sideband events K (*) e  events cut

Peaking Background: Reduction and Estimation Backgrounds with the same shape in (m ES,  E) as signal Veto most of it, estimate the rest from MC and control samples B Decays to J/  K (*),  ’ K (*) B Decays to h + h - K (*) 500 fb -1 MC Veto events in the (m ll,  E) plane Residual bkgrd. from fit to charmonium MC J/  veto  ’ veto h + h - K (*) events in data convolved with rates for h to fake e,  D to  K (*)  events vetoed for K (*)  modes 0.01 events0.33 events