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

DOE SITE VISIT

Thursday, June 18, 2009

Bruce A. SchummSanta Cruz Institute for Particle Physics

University of California, Santa Cruz

BaBar

BaBar Radiative Penguin BaBar Radiative Penguin Physics at SCIPPPhysics at SCIPP

2009 DOE Site Visit 2Bruce SchummBaBar

PeoplePeople

SeniorAl Eisner (b s)

Bruce Schumm

Post-DoctoralJuergen 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)


OutlineOutline

Effective Neutral Currents: General Motivation

b s PenguinsSUSY parameter space implications

b s “Inclusive” approach

b d Penguins and |Vtd/Vts|

Motivation

B →(ρ,ω)“Exclusive” approach

B→Xd “Semi-Inclusive” approach

CP Violation in B →ρo

Conclusions


Effective Neutral Currents and Radiative PenguinsEffective Neutral Currents and Radiative Penguins

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.

Vtb Vt(s,d)

(d) (d) (d)


OutlineOutline


b sSUSY parameter space implications

Inclusive approach

b d and |Vtd/Vts|

Motivation

B →(ρ,ω)(“Standard” Approach)

B→Xd (“Semi-Inclusive” Approach)

Status of |Vtd/Vts|

CP Violation in B00

Conclusions


B B s s and SUSY Parameter Space 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)


The eThe e++ee-- Cross Section in the Upsilon Region Cross Section in the Upsilon Region

bbOn-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 ) 00BBBB

bb


B Factory Data SetsB Factory Data Sets

700 fb-1

440 fb-1


Inclusive Measurement of b Inclusive Measurement of b s s: Introduction: Introduction

qq + ττ

BB

XSγ

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


Inclusive Measurement of b Inclusive Measurement of b s s: Signal/Background: Signal/Background

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


Inclusive Measurement of b Inclusive Measurement of b s s: : 00,, Backgrounds Backgrounds

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, …

Major source of BB background due to high-energy photons from 0() (67% + 15% = 82% of total BB background according to MC)


Summary of Measurements of the b Summary of Measurements of the b s s Rate Rate

Collaborating with SLAC, Notre Dame; SCIPP playing central role since 2003 (Schmitz thesis, Winstrom candidacy project)

Inclusive

Semi-Inclusive

Inclusive

Inclusive

Inclusive

A. Limosani, Melbourne

BaBar Result on 360 fb-1 expected by end of year


OutlineOutline


b sSUSY parameter space implications

Inclusive approach

b d and |Vtd/Vts|

Motivation

B →(ρ,ω)(“Standard” Approach)

B→Xd (“Semi-Inclusive” Approach)

Status of |Vtd/Vts|

CP Violation in B00

Conclusions


Measuring |VMeasuring |Vtdtd/V/Vtsts||

(d) (d)(d)

(d)

(d)

(d)

Vt(s,d)Note: In both cases, hadronic

uncertainties minimized by comparing to corresponding Vts

process (Bs mixing, b s)

Observable is | Vtd / Vts |

B Mixing

Radiative Penguins

Two independent diagrams provide sensitivity to CKM

parameter Vtd


|V|Vtdtd/V/Vtsts| from Penguins: Motivation| from Penguins: Motivation

ICHEP ’08 B Mixing Results [Farrington(CDF), Moulik(D0), averaged by Di Lodovico (BaBar)]:

How do penguins fit into the picture?

Mixing: xd = mB/B ~ 1 mB ~ B

Penguins: Br(bd) ~ 10-5 d ~ 10-5 B

With |Vtd/Vts| precisely constrained by mixing, b d is a compelling testbed for

new physics.

SM effects suppressed

by 10-5 relative to

mixing


Exclusive Approach: B Exclusive Approach: B (() )

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/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|.

Annihilation Diagram


Measurement of Measurement of BB(B (B (() ) ) (continued)) (continued)

2*2*BbeamES pEM

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

*In e+e- CMS frame

EB = Ebeam for properly reconstructed candidate; total energy measurement

2*2*

BbeamESpEM

***

beamBEEE

Example: BaBar B0 0 “self-calibrating” continuum background subtraction

efficiencies (~5-15%) estimated with control samples

SignalContinuum

bs Feedthrough


|V|Vtdtd/V/Vtsts| from Exclusive (| from Exclusive (,,) Decays) Decays

yielding70.3

8.210)6.13.16()),((B

B022.0025.0021.0024.0

233.0|/|

tstdVV

assuming the world-average 5* 10)17.016.4()(B KB

Phys.Rev.D78:112001,2008

Mode BaBar ’07 (x10-7) BaBar ’08 (x10-7)

+ 0

6.07.9 4.2

2.2

0.20.12 2.4

7.3

9.00.11 7.3

3.3

6.09.7 2.2

0.2

9.00.5 7.2

3.2

5.00.4 4.2

0.2

BaBar: 423 fb-1 Phys.Rev.D78:112001,2008

Collaborating with CALTECH; SCIPP contribution data processing, validation, systematics (Spradlin thesis, Martinez candidacy project)


Semi-Inclusive Approach: B Semi-Inclusive Approach: B X Xdd (Preliminary) (Preliminary)

|Vtd/Vts|2 related to (bd)/(bs) with ~1% theoretical uncertainty [Ali, Asatrian, Greub, Phys. Lett. B 429, 87 (1998)]

“New” Approach (BaBar): Reconstruct seven exclusive final states Xd in range 0.6 GeV/c2 < MXd < 1.8 GeV/c2

Collaborating with Imperial College, London; SCIPP playing central role since inception (Beck thesis)


Measured Regions for B Measured Regions for B X Xd(s)d(s)

K* Region

1.0 < Mhad < 1.8 1.8 < Mhad

XS

Xd

MEASURED

UNMEASURED

and Xd analyses

Xd analysis only

Mhad (MXd)

# 0

# bodies

# 0

# bodies

MEASURED

UNMEASURED

0.6 < Mhad < 1.0


B B X X(s,d)(s,d) Decay Width Ratio Results 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


Calculation of |VCalculation of |Vtdtd/V/Vtsts||

arXiv:0807.4975 [hep-ex]; to appear in PRL

Ali

Asatrian

Greub

)(

)(

sb

db

009.0013.0033.0

|/| tstd VV

001.0043.0177.0

Expt. Theory

Ratio of partial widths related to |Vtd/Vts| with very small uncertaintys


Global Status of |VGlobal Status of |Vtdtd/V/Vtsts||

No evidence for non-Standard-Model contribution to the b d decay width.

Is the implication of this constraint fully understood?


CP Violation in BCP Violation in B00 00

Separate out B0 (“+”) and anti-B0 (“-”) decays; look at asymmetry in time-evolution:


00 CP Violation Sensitivity Study CP Violation Sensitivity Study

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


Concluding RemarksConcluding 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 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; 5th on the way; recent talks at CKM’08, Miami’08, FNAL Wine & Cheese, DESY Exptl Seminar


Backup Slides


Inclusive Measurement of b Inclusive Measurement of b s s: B/Bbar Backgrounds: B/Bbar Backgrounds

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% 0.4%

Total 92.8% 92.4%

e Any 4.8% 3.7%

n/nbar Any 1.7% 2.9%

p+/p- Any 0.0% 0.1%

/K Any 0.4% 0.8%

Total non- 7.2% 7.6%

Total 100% 100%

Sources of B/Bbar Background (after full selection)


cosh

Inclusive Measurement of b Inclusive Measurement of b s s: : 00,, Backgrounds Backgrounds

Define cosh (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 ()/()E

xpec

ted/

Mea

sure

d

cosh

But: can bootstrap to lower E with dedicated 0 sample


BX(d,s): Correction for Missing Modes

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

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 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 XS Resonances

• K1 (1270)• K1 (1400)• K* (1410)• K2

*(1430)• K* (1680)

B Xd Resonances

• h10 (1170)

• b10 (1235)

• b1+ (1235)

• a10 (1260)

• a1+ (1260)

• f20 (1270)

• f10 (1285)

• a20 (1320)

• a2+ (1320)

BX(d,s): Correction for Missing Modes

Documents

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