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

2009 DOE Site Visit2 Bruce Schumm Senior Al Eisner (b  s  ) Bruce Schumm Post-Doctoral 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)

BaBar 2009 DOE Site Visit3 Bruce Schumm Effective Neutral Currents: General Motivation b  s  Penguins SUSY parameter space implications b  s  “Inclusive” approach b  d  Penguins and |V td /V ts | Motivation B →  (ρ,ω)  “Exclusive” approach B  →  X d “Semi-Inclusive” approach CP Violation in B →  ρ o  Conclusions

BaBar 2009 DOE Site Visit4 Bruce Schumm so new physics can enter at leading order: The SM b  s(d)  transition is high order (two weak plus one EM vertex) … + photon off any charged leg Although rare (~ 5x10 -4 for s  and ~10 -5 for d  ), the isolated high-energy photon is a powerful signature. V tb V t(s,d) (d)

BaBar 2009 DOE Site Visit5 Bruce Schumm Effective Neutral Currents: General Motivation b  s  SUSY parameter space implications Inclusive approach b  d  and |V td /V ts | Motivation B →  (ρ,ω)  (“Standard” Approach) B  →  X d (“Semi-Inclusive” Approach) Status of |V td /V ts | CP Violation in B 0  0  Conclusions

BaBar 2009 DOE Site Visit6 Bruce Schumm C.F. BergerC.F. Berger, J.S. Gainer, J.L. Hewett, T.G. Rizzo,J.S. GainerJ.L. HewettT.G. Rizzo “Supersymmetry Without Prejudice”, arXiv: v1 [hep-ph]arXiv: v1 Explore 10 7 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)

BaBar 2009 DOE Site Visit7 Bruce Schumm On-Peak Data Off-Peak Data (~10% of Sample)  (4S) resonance is ~1 nb at peak, competing with a “continuum” background of ~3 nb The  (4S) resonance is the lightest resonance that decays into “open Beauty” ( or )

BaBar 2009 DOE Site Visit8 Bruce Schumm 700 fb fb -1

BaBar 2009 DOE Site Visit9 Bruce Schumm qq + ττ BB XSγXSγ 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

BaBar 2009 DOE Site Visit10 Bruce Schumm B/Bbar background control region BB Cont. Signal Sig. Region After event selection, S/B is roughly 1:1 Continuum measured from below-peak running B/Bbar backgrounds must be identified and constrained

BaBar 2009 DOE Site Visit11 Bruce Schumm   If high-energy  passes selection, then look for low-energy  and veto event 0,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, … Major source of BB background due to high-energy photons from  0 (  )   (67% + 15% = 82% of total BB background according to MC)

BaBar 2009 DOE Site Visit12 Bruce Schumm Collaborating with SLAC, Notre Dame; SCIPP playing central role since 2003 (Schmitz thesis, Winstrom candidacy project) Inclusive Semi-Inclusive Inclusive A. Limosani, Melbourne BaBar Result on 360 fb -1 expected by end of year

BaBar 2009 DOE Site Visit13 Bruce Schumm Effective Neutral Currents: General Motivation b  s  SUSY parameter space implications Inclusive approach b  d  and |V td /V ts | Motivation B →  (ρ,ω)  (“Standard” Approach) B  →  X d (“Semi-Inclusive” Approach) Status of |V td /V ts | CP Violation in B 0  0  Conclusions

BaBar 2009 DOE Site Visit14 Bruce Schumm (d) V t(s,d) Note: In both cases, hadronic uncertainties minimized by comparing to corresponding V ts process (B s mixing, b  s  )  Observable is | V td / V ts | B Mixing Radiative Penguins Two independent diagrams provide sensitivity to CKM parameter V td

BaBar 2009 DOE Site Visit15 Bruce Schumm ICHEP ’08 B Mixing Results [Farrington(CDF), Moulik(D0), averaged by Di Lodovico (BaBar)]: How do penguins fit into the picture? Mixing: x d =  m B /  B ~ 1   m B ~  B Penguins: Br(b  d  ) ~   d  ~  B With |V td /V ts | precisely constrained by mixing, b  d  is a compelling testbed for new physics. SM effects suppressed by relative to mixing

BaBar 2009 DOE Site Visit16 Bruce Schumm Standard (“Exclusive”) Approach: measure exclusive rate Br(B   (  )  ); normalize with Br(B  K *  ) (and  ) Values of  2 and  R are available from Ali, Parkhomenko, arXiv:hep-ph/ Ball, Zwicky, J. High. Energy Phys. 0604, 046 (2006); Ball, Jones, Zwicky, Phys. Rev. D (2007)  8% uncertainty on extraction of |V td /V ts |. Annihilation Diagram

BaBar 2009 DOE Site Visit17 Bruce Schumm Remaining separation achieved by two-dimensional fit to the largely independent kinematic variables “Energy-substituted mass”; since E beam ~ M B, largely a measurement of momentum balance * In e + e - CMS frame E B = E beam for properly reconstructed candidate; total energy measurement Example: BaBar B 0   0   “self-calibrating” continuum background subtraction  efficiencies (~5-15%) estimated with control samples Signal Continuum b  s  Feedthrough

BaBar 2009 DOE Site Visit18 Bruce Schumm yielding assuming the world-average Phys.Rev.D78:112001,2008 ModeBaBar ’07 (x10 -7 )BaBar ’08 (x10 -7 ) + +  0 0     BaBar:  423 fb -1 Phys.Rev.D78:112001,2008 Collaborating with CALTECH; SCIPP contribution data processing, validation, systematics (Spradlin thesis, Martinez candidacy project)

BaBar 2009 DOE Site Visit19 Bruce Schumm |V td /V ts | 2 related to  (b  d  )/  (b  s  ) with ~1% theoretical uncertainty [ Ali, Asatrian, Greub, Phys. Lett. B 429, 87 (1998) ] “New” Approach (BaBar): Reconstruct seven exclusive final states X d  in range 0.6 GeV/c 2 < M Xd < 1.8 GeV/c 2 Collaborating with Imperial College, London; SCIPP playing central role since inception (Beck thesis)

BaBar 2009 DOE Site Visit20 Bruce Schumm K * Region 1.0 < M had < < M had XSXS XdXd MEASURED UNMEASURED  and X d analyses X d analysis only M had (M Xd ) #  0 # bodies #  0 # bodies MEASURED UNMEASURED 0.6 < M had < 1.0

BaBar 2009 DOE Site Visit21 Bruce Schumm Fit in high-mass X d  region 1.0 < M had < 1.8 GeV/c 2 Continuum background X s , MisID background B A B AR EEM ES Errors: Stat.  Experimental Syst. Primary experimental result arXiv: [hep-ex]; to appear in PRL

BaBar 2009 DOE Site Visit22 Bruce Schumm arXiv: [hep-ex]; to appear in PRL Ali Asatrian Greub Expt. Theory Ratio of partial widths related to |V td /V ts | with very small uncertaintys

BaBar 2009 DOE Site Visit23 Bruce Schumm No evidence for non-Standard-Model contribution to the b  d  decay width. Is the implication of this constraint fully understood?

BaBar 2009 DOE Site Visit24 Bruce Schumm Separate out B 0 (“+”) and anti-B 0 (“-”) decays; look at asymmetry in time-evolution:

BaBar 2009 DOE Site Visit25 Bruce Schumm Collaborating with SLAC; SCIPP playing central role since inception (Martinez thesis topic) 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

BaBar 2009 DOE Site Visit26 Bruce Schumm  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  One PRL, one PRD in last year * 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; 5 th on the way; recent talks at CKM’08, Miami’08, FNAL Wine & Cheese, DESY Exptl Seminar

BaBar 2009 DOE Site Visit27 Bruce Schumm Backup Slides

BaBar 2009 DOE Site Visit28 Bruce Schumm ObjectSourceControl RegionSignal Region 00 57.3%66.6%  17.1%15.7%  Other meson8.7%5.1%  e9.3%4.7%  Other0.4% Total  92.8%92.4% eAny4.8%3.7% n/n bar Any1.7%2.9% p + /p - Any0.0%0.1%  /K Any0.4%0.8% Total non-  7.2%7.6% Total100% Sources of B/Bbar Background (after full selection)

BaBar 2009 DOE Site Visit29 Bruce Schumm cos  h 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 2 nd photon down.  Sensitive to reconstruction efficiency for MeV photons. Measurement of  0 reconstruction efficiency from (  )/(  ) Expected/Measured cos  h But: can bootstrap to lower E  with dedicated  0 sample

BaBar 2009 DOE Site Visit30 Bruce Schumm B  X (d,s)  : Correction for Missing Modes Missing modes with 0.6 < M X < 1.0 MC suggests this region is dominated by resonances (  and  ); confirmed by K* dominance of B  X s  Correction for missing modes well understood MC Simulation Two-body X s(d)  decay; mass spectrum of X s(d) system given by Kagan-Neubert model A.L. Kagan, M. Neubert, Phys. Rev. D 58, (1998) Fragment X s system via prior experimental constraint Fragment X d system via phase space

BaBar 2009 DOE Site Visit31 Bruce Schumm Missing Modes with 1.0 < M X < 1.8 Force 50% of decays to un-weighted mix of higher-mass resonances Force X d decay to be identical to X s decay up to substitution s  d B  X S  Resonances K 1 (1270) K 1 (1400) K * (1410) K 2 * (1430) K * (1680) B  X d  Resonances h 1 0 (1170) b 1 0 (1235) b 1 + (1235) a 1 0 (1260) a 1 + (1260) f 2 0 (1270) f 1 0 (1285) a 2 0 (1320) a 2 + (1320) B  X (d,s)  : Correction for Missing Modes