DOE SITE VISIT Monday, July 27, 2011 Bruce A. Schumm Santa Cruz Institute for Particle Physics...

DOE SITE VISIT

Monday, July 27, 2011

Bruce A. SchummSanta Cruz Institute for Particle Physics

University of California, Santa Cruz

BaBar

BaBar Radiative BaBar Radiative Penguin Physics at SCIPPPenguin Physics at SCIPP

2010 DOE Site Visit 2Bruce SchummBaBar

PeoplePeople

SeniorAl Eisner (volunteer)Bruce Schumm

StudentJoel Martinez (B Ph.D. expected 9/2011)

Post-docWilliam Panduro-Vazquez (volunteer; now an ATLAS postdoc at)


OutlineOutline

Effective Neutral Currents: General Motivation

b s PenguinsSUSY parameter space implications

b s “Inclusive” approach

b d Penguins and |Vtd/Vts|

Motivation

B→Xd “Semi-Inclusive” approach

Status of |Vtd/Vts|

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→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)


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

Most prominent SCIPP Contributions:

• 0, rejection and backgrounds

• Anti-neutron backgrounds

• BAD editor (Eisner)


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 is finalized:


Expected Errors (all major uncertainties included) Expected Errors (all major uncertainties included)

Branching Fraction Results (x 104)

Quoted errors: (stat%) (syst%)

BABAR Runs I-V

E* > 2.0 2.80 0.12 0.14

6.6%

E* > 1.9 3.00 0.14 0.19

7.9%

E* > 1.8 3.20 0.15 0.29

10.2%

BELLE 605 fb-1

E* > 1.8 3.24 0.17 0.24 9.1 %

Expect to quote preliminary result for E* > 1.8 this

summer (ICHEP)


Unblinded Spectrum (not yet public)Unblinded Spectrum (not yet public)

E*

Sig

nal P

hoto

ns p

er

0.1

GeV

NOT YET PUBLIC

SIGNAL REGION

Runs I-V

But: Predictions are in B rest frame unfolddetector smearing and boosts…


Unfolded Spectrum (also not yet public)Unfolded Spectrum (also not yet public)

Largest effect is boost at kinematic edge.

Nearing review-board approval (!!) Phys. Rev. D article in prepartation

Sig

nal P

hoto

ns p

er

0.1

GeV

Ecms

Procedure: An iterative, dynamically-stabilized method of data unfolding, B. Malaescu, ArXiv 0907:3791


OutlineOutline


b sSUSY parameter space implications

Inclusive approach

b d and |Vtd/Vts|

Motivation

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


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)]

Alternative Approach (Runs I-V): Reconstruct seven exclusive final states Xd in range 0.6 GeV/c2 < MXd < 1.8 GeV/c2 ( now published in PRL 102:161803,2009

Collaborating with I.C. London & SLAC New: Include Run VI, re-optimize event selection; extend MXd to 2.0 GeV/c2


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

K* Region

1.0 < Mhad < 2.0 2.0 < 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 < 2.0 GeV/c2

E MES

BABAR PRELIMINARY

First significant observation of b d above resonant region

Primary Exptl Result (prior result: 0.033 0.013 0.009);Submitted to PRL


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

Submitted to PRL

Ali

Asatrian

Greub

)(

)(

sb

db

010.0009.0040.0

|/| tstd VV

001.0032.0199.0

Expt. Theory

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

BABAR PRELIMINARY


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

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

Starting to receive attention from theory community: Crivellin, Mecolli,“B Xd and Constraints on New Physics” arXiv:1106.5499

Published Sept 2010: Phys.Rev.D82:051101


Review of Radiative Penguin Transition RatesReview of Radiative Penguin Transition Rates

Invited review:

Radiative Penguin transition rates (published in Modern Physics Letters A, August 2010)

Invited talk:

2011 Lake Louise Winter Institute


CP Violation in BCP Violation in B00 00

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

Standard Model expectation: C = -0.1 and S = 0 (due to phase cancellation between mixing and t-quark-dominated decay)


00 expected signal and background expected signal and background

Significant signal-region backgrounds are:

• Continuum• Generic B• K-

Small fraction of non-truth-matched signal (no special treatment)

MODE Expected # events (440 fb-1)

Truth-matched signal 41.6

Non-truth-matched signal 8.7

Continuum 1734

+ 0.5

0.7

K+ - 17.6

K+ 0 0.3

K0S - 15.2

K0S 0 0.0

B0B0 59.0

B+B- 44.2


00 signal kinematic distributions signal kinematic distributions

tdE MES


ss background kinematic distributions background kinematic distributions

tdE MES

K+-

K0S-

Displaced; broad

Broader tail


00 expected signal and background expected signal and background

Significant

dE MES t

B+B-

B0B0


Continuum kinematic distributionsContinuum kinematic distributions

t

dE MES

Fit components:

• Signal • Continuum• Generic B• K+-

• K0S-


Fitting strategyFitting strategy

Plan to employ a two-stage fit:

1)Fit over full region in dE and MES (ignore t) to establish continuum and normalization and shape and signal normalization

2)Fit over signal region (including t) to extract S, C, fixing continuum and signal parameters to the values obtained in 1).


00 CP Violation First-Stage Fit CP Violation First-Stage Fit

Fit for Nsig: <N> = 50 19 <PULL> = -0.07 0.03


00 CP Violation Second-Stage Fit CP Violation Second-Stage Fit

Fit for S,C: <S> = 0.47 <PULLS> = 0.01 0.03


Concluding RemarksConcluding Remarks

SCIPP playing central role in key radiative penguin measurements

Inclusive b s measurement very challenging; drafting long PRD with 10% (E

* > 1.8 GeV) (prior result was 14.5% for E

* > 1.9 GeV)

Intensive focus on b d transition* Rates Three PRL, one PRD in last three years* CP Violation Expect result in ~6 months

First observation of non-resonant b d transition (Impact of b d signature may not yet be fully appreciated)

Schumm wrote s(d) review article for World Scientific

5 PhD theses; 6th on the way


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)


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)


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

DOE SITE VISIT Monday, July 27, 2011 Bruce A. Schumm Santa Cruz Institute for Particle Physics...

Documents

Transcript of DOE SITE VISIT Monday, July 27, 2011 Bruce A. Schumm Santa Cruz Institute for Particle Physics...