BaBar Radiative Penguin Physics at SCIPP DOE SITE VISIT Thursday, June 18, 2009 BaBar BaBar Radiative Penguin Physics at SCIPP Bruce A. Schumm Santa Cruz Institute for Particle Physics University of California, Santa Cruz

Senior Post-Doctoral Students People Al Eisner (b  s) Bruce Schumm Juergen Kroseberg (RadPen Convener; to U. Bonn 2/08) Students Patrick Spradlin (B   Ph.D. June 2007; Oxford P.D.) Tim Beck (b  d Ph.D. June 2008; college teaching) Luke Winstrom (Ph.D. June 2009; many P.D. offers) Joel Martinez (B   Ph.D. expected June 2010) Bruce Schumm 2009 DOE Site Visit

Effective Neutral Currents: General Motivation b  s Penguins Outline Effective Neutral Currents: General Motivation b  s Penguins SUSY parameter space implications b  s “Inclusive” approach b  d Penguins and |Vtd/Vts| Motivation B → (ρ,ω)g “Exclusive” approach B → Xd “Semi-Inclusive” approach CP Violation in B → ρo g Conclusions Bruce Schumm 2009 DOE Site Visit

Effective Neutral Currents and Radiative Penguins The SM b  s(d)  transition is high order (two weak plus one EM vertex) … Vtb Vt(s,d) so new physics can enter at leading order: + photon off any charged leg (d) (d) (d) Although rare (~ 5x10-4 for s and ~10-5 for d), the isolated high-energy photon is a powerful signature. Bruce Schumm 2009 DOE Site Visit

Effective Neutral Currents: General Motivation b  s Outline Effective Neutral Currents: General Motivation b  s SUSY parameter space implications Inclusive approach b  d and |Vtd/Vts| Motivation B → (ρ,ω)g (“Standard” Approach) B → Xd (“Semi-Inclusive” Approach) Status of |Vtd/Vts| CP Violation in B00 Conclusions Bruce Schumm 2009 DOE Site Visit

B  s and SUSY Parameter Space C.F. Berger, J.S. Gainer, J.L. Hewett, T.G. Rizzo, “Supersymmetry Without Prejudice”, arXiv:0812.0980v1 [hep-ph] Explore 107 points over 19-dimensional parameter space of CP-conserving MSSM b  s most effective constraint (72% of models surviving prior constraints are eliminated; better than direct searches for SUSY partners) Bruce Schumm 2009 DOE Site Visit

The e+e- Cross Section in the Upsilon Region The (4S) resonance is the lightest resonance that decays into “open Beauty” ( or ) Off-Peak Data (~10% of Sample) On-Peak Data (4S) resonance is ~1 nb at peak, competing with a “continuum” background of ~3 nb Bruce Schumm 2009 DOE Site Visit

B Factory Data Sets 440 fb-1 700 fb-1 For FNAL: Add detector slides here! Bruce Schumm 2009 DOE Site Visit

Inclusive Measurement of b  s: Introduction Most exacting approach (“Inclusive”) is aggressive: Use only high-energy  as signature Suppress continuum with event shapes, requirement of a high-energy lepton. Estimate remaining continuum by scaling off-peak data. Challenge: background from 0()   decays (plus some fakes) in B decays qq + ττ BB XSγ Note: Here, might want to go into history (P. Kim) a bit, and motivate fully inclusive approach. Bruce Schumm 2009 DOE Site Visit

Inclusive Measurement of b  s: Signal/Background Sig. Region B/Bbar background control region BB Cont. Signal After event selection, S/B is roughly 1:1 Continuum measured from below-peak running B/Bbar backgrounds must be identified and constrained (e.g. ~1% understanding of CAL response at 30-80 MeV) Bruce Schumm 2009 DOE Site Visit

Summary of Measurements of the b  s Rate Collaborating with SLAC, Notre Dame; SCIPP playing central role since 2003 (Schmitz thesis, Winstrom candidacy project) A. Limosani, Melbourne Inclusive Semi-Inclusive BaBar Result on 360 fb-1 expected by end of year Bruce Schumm 2009 DOE Site Visit

Effective Neutral Currents: General Motivation b  s Outline Effective Neutral Currents: General Motivation b  s SUSY parameter space implications Inclusive approach b  d and |Vtd/Vts| Motivation B → (ρ,ω)g (“Standard” Approach) B → Xd (“Semi-Inclusive” Approach) Status of |Vtd/Vts| CP Violation in B00 Conclusions Bruce Schumm 2009 DOE Site Visit

Two independent diagrams provide sensitivity to CKM parameter Vtd Measuring |Vtd/Vts| Two independent diagrams provide sensitivity to CKM parameter Vtd (d) B Mixing Vt(s,d) Note: In both cases, hadronic uncertainties minimized by comparing to corresponding Vts process (Bs mixing, b  s)  Observable is | Vtd / Vts | Radiative Penguins Bruce Schumm 2009 DOE Site Visit

|Vtd/Vts| from Penguins: Motivation ICHEP ’08 B Mixing Results [Farrington(CDF), Moulik(D0), averaged by Di Lodovico (BaBar)]: How do penguins fit into the picture? SM effects suppressed by 10-5 relative to mixing Mixing: xd = mB/B ~ 1  mB ~ B Penguins: Br(bd) ~ 10-5  d ~ 10-5 B With |Vtd/Vts| precisely constrained by mixing, b  d is a compelling testbed for new physics. Bruce Schumm 2009 DOE Site Visit

Exclusive Approach: B  ()  Standard (“Exclusive”) Approach: measure exclusive rate Br(B  () ); normalize with Br(B  K* ) (and ) Annihilation Diagram Values of 2 and R are available from Ali, Parkhomenko, arXiv:hep-ph/0610149 Ball, Zwicky, J. High. Energy Phys. 0604, 046 (2006); Ball, Jones, Zwicky, Phys. Rev. D 75 054004 (2007)  8% uncertainty on extraction of |Vtd/Vts|. Bruce Schumm 2009 DOE Site Visit

Measurement of B(B  () ) (continued) Remaining separation achieved by two-dimensional fit to the largely independent kinematic variables “Energy-substituted mass”; since Ebeam ~ MB, largely a measurement of momentum balance EB = Ebeam for properly reconstructed candidate; total energy measurement *In e+e- CMS frame Example: BaBar B0  0  “self-calibrating” continuum background subtraction efficiencies (~5-15%) estimated with control samples Continuum Signal bs Feedthrough Bruce Schumm 2009 DOE Site Visit

|Vtd/Vts| from Exclusive (,) Decays BaBar ‘07:  330 fb-1 Phys.Rev.Lett.98:151802,2007 BaBar ‘08:  423 fb-1 Phys.Rev.D78:112001,2008 Mode BaBar ’07 (x10-7) BaBar ’08 (x10-7) +  0    yielding Phys.Rev.D78:112001,2008 Collaborating with CALTECH; SCIPP contribution data processing, validation, systematics (Spradlin thesis, Martinez candidacy project) Bruce Schumm 2009 DOE Site Visit

Semi-Inclusive Approach: B  Xd  (Preliminary) “New” Approach (BaBar): Reconstruct seven exclusive final states Xd in range 0.6 GeV/c2 < MXd < 1.8 GeV/c2 |Vtd/Vts|2 related to (bd)/(bs) with ~1% theoretical uncertainty [Ali, Asatrian, Greub, Phys. Lett. B 429, 87 (1998)] Collaborating with Imperial College, London; SCIPP playing central role since inception (Beck thesis) Bruce Schumm 2009 DOE Site Visit

Measured Regions for B  Xd(s)  # 0 UNMEASURED XS MEASURED K* Region # bodies 0.6 < Mhad < 1.0 1.0 < Mhad < 1.8 1.8 < Mhad # bodies # 0 UNMEASURED Xd MEASURED Xd analysis only  and Xd analyses Mhad (MXd) Bruce Schumm 2009 DOE Site Visit

B  X(s,d)  Decay Width Ratio Results Fit in high-mass Xd  region 1.0 < Mhad < 1.8 GeV/c2 Continuum background Xs, MisID background BABAR BABAR E MES Errors: Stat.  Experimental Syst. Primary experimental result arXiv:0807.4975 [hep-ex]; to appear in PRL Bruce Schumm 2009 DOE Site Visit

Calculation of |Vtd/Vts| arXiv:0807.4975 [hep-ex]; to appear in PRL Ali Asatrian Greub Expt. Theory Ratio of partial widths related to |Vtd/Vts| with very small uncertaintys Bruce Schumm 2009 DOE Site Visit

Global Status of |Vtd/Vts| No evidence for non-Standard-Model contribution to the b  d decay width. Is the implication of this constraint fully understood? Bruce Schumm 2009 DOE Site Visit

CP Violation in B0 0 Separate out B0 (“+”) and anti-B0 (“-”) decays; look at asymmetry in time-evolution: Bruce Schumm 2009 DOE Site Visit

0 CP Violation Sensitivity Study Toy Monte Carlo study based on Br(B) selection S SENSITIVITY SIGNAL SIGNIFICANCE vs. Event Selection Parameter (“Decision Tree” Output) Full re-optimization nearing completion; next step will be to confirm fitting strategy and identify leading systematics Collaborating with SLAC; SCIPP playing central role since inception (Martinez thesis topic) Bruce Schumm 2009 DOE Site Visit

Intensive focus on b  d transition Concluding Remarks SCIPP playing central role in key, high-impact radiative penguin measurements Inclusive b  s measurement very challenging; expect to have result to better than 10% in ~6 months Intensive focus on b  d transition * Rates  Two PRL, one PRD in last two years * CP Violation  Expect result in ~1 year Ground-breaking semi-inclusive b  d measurement promising for higher-statistics running Impact of b  d signature may not yet be fully appreciated 4 PhD theses; 5th on the way; recent talks at CKM’08, Miami’08, FNAL Wine & Cheese, DESY Exptl Seminar Bruce Schumm 2009 DOE Site Visit

Backup Slides Bruce Schumm 2009 DOE Site Visit

Inclusive Measurement of b  s: B/Bbar Backgrounds Sources of B/Bbar Background (after full selection) Object Source Control Region Signal Region  0 57.3% 66.6%  17.1% 15.7% Other meson 8.7% 5.1% e 9.3% 4.7% Other 0.4% Total  92.8% 92.4% Any 4.8% 3.7% n/nbar 1.7% 2.9% p+/p- 0.0% 0.1% /K 0.8% Total non-  7.2% 7.6% Total 100% Bruce Schumm 2009 DOE Site Visit

Inclusive Measurement of b  s: 0, Backgrounds Major source of BB background due to high-energy photons from 0()   (67% + 15% = 82% of total BB background according to MC)  If high-energy  passes selection, then look for low-energy  and veto event 0, ~50% of the time the low-energy photon is missing. Modeling of low-energy (30-80 MeV) photon efficiency to ~ 1% critical to lowering systematic error One example of SCIPP group contribution Also: Anti-neutron backgrounds, photon efficiency, … Bruce Schumm 2009 DOE Site Visit

Inclusive Measurement of b  s: 0, Backgrounds Define cosh  (E,high - E,low)/ (E,high + E,low) = energy asymmetry Signal selection requirement of E* > 1.8 GeV pushes asymmetry up, and energy of 2nd photon down.  Sensitive to reconstruction efficiency for 30-80 MeV photons. Measurement of 0 reconstruction efficiency from ()/() Expected/Measured cosh cosh But: can bootstrap to lower E with dedicated 0 sample Bruce Schumm 2009 DOE Site Visit

A.L. Kagan, M. Neubert, Phys. Rev. D 58, 094012 (1998) BX(d,s): Correction for Missing Modes MC Simulation Two-body Xs(d)  decay; mass spectrum of Xs(d) system given by Kagan-Neubert model A.L. Kagan, M. Neubert, Phys. Rev. D 58, 094012 (1998) Fragment Xs system via prior experimental constraint Fragment Xd system via phase space Missing modes with 0.6 < MX < 1.0 MC suggests this region is dominated by resonances ( and ); confirmed by K* dominance of B Xs Correction for missing modes well understood Bruce Schumm 2009 DOE Site Visit

BX(d,s): Correction for Missing Modes Missing Modes with 1.0 < MX < 1.8 Force 50% of decays to un-weighted mix of higher-mass resonances Force Xd decay to be identical to Xs decay up to substitution s  d B  Xd  Resonances h10 (1170) b10 (1235) b1+ (1235) a10 (1260) a1+ (1260) f20 (1270) f10 (1285) a20 (1320) a2+ (1320) B  XS  Resonances K1 (1270) K1 (1400) K* (1410) K2*(1430) K* (1680) Bruce Schumm 2009 DOE Site Visit