doe site visit monday, july 27, 2011 bruce a. schumm santa cruz institute for particle physics...
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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)
2010 DOE Site Visit 3Bruce SchummBaBar
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
2010 DOE Site Visit 4Bruce SchummBaBar
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)
2010 DOE Site Visit 5Bruce SchummBaBar
OutlineOutline
Effective Neutral Currents: General Motivation
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
2010 DOE Site Visit 6Bruce SchummBaBar
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)
2010 DOE Site Visit 7Bruce SchummBaBar
B Factory Data SetsB Factory Data Sets
700 fb-1
440 fb-1
2010 DOE Site Visit 8Bruce SchummBaBar
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
2010 DOE Site Visit 9Bruce SchummBaBar
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)
2010 DOE Site Visit 10Bruce SchummBaBar
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:
2010 DOE Site Visit 11Bruce SchummBaBar
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)
2010 DOE Site Visit 12Bruce SchummBaBar
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…
2010 DOE Site Visit 13Bruce SchummBaBar
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
2010 DOE Site Visit 14Bruce SchummBaBar
OutlineOutline
Effective Neutral Currents: General Motivation
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
2010 DOE Site Visit 15Bruce SchummBaBar
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
2010 DOE Site Visit 16Bruce SchummBaBar
|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
2010 DOE Site Visit 17Bruce SchummBaBar
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
2010 DOE Site Visit 18Bruce SchummBaBar
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
2010 DOE Site Visit 19Bruce SchummBaBar
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
2010 DOE Site Visit 20Bruce SchummBaBar
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
2010 DOE Site Visit 21Bruce SchummBaBar
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
2010 DOE Site Visit 22Bruce SchummBaBar
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
2010 DOE Site Visit 23Bruce SchummBaBar
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
2010 DOE Site Visit 24Bruce SchummBaBar
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)
2010 DOE Site Visit 25Bruce SchummBaBar
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
2010 DOE Site Visit 26Bruce SchummBaBar
00 signal kinematic distributions signal kinematic distributions
tdE MES
2010 DOE Site Visit 27Bruce SchummBaBar
ss background kinematic distributions background kinematic distributions
tdE MES
K+-
K0S-
Displaced; broad
Broader tail
2010 DOE Site Visit 28Bruce SchummBaBar
00 expected signal and background expected signal and background
Significant
dE MES t
B+B-
B0B0
2010 DOE Site Visit 29Bruce SchummBaBar
Continuum kinematic distributionsContinuum kinematic distributions
t
dE MES
Fit components:
• Signal • Continuum• Generic B• K+-
• K0S-
2010 DOE Site Visit 30Bruce SchummBaBar
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).
2010 DOE Site Visit 31Bruce SchummBaBar
00 CP Violation First-Stage Fit CP Violation First-Stage Fit
Fit for Nsig: <N> = 50 19 <PULL> = -0.07 0.03
2010 DOE Site Visit 32Bruce SchummBaBar
00 CP Violation Second-Stage Fit CP Violation Second-Stage Fit
Fit for S,C: <S> = 0.47 <PULLS> = 0.01 0.03
2010 DOE Site Visit 33Bruce SchummBaBar
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
2010 DOE Site Visit 34Bruce SchummBaBar
Backup Slides
2010 DOE Site Visit 35Bruce SchummBaBar
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)
2010 DOE Site Visit 36Bruce SchummBaBar
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)
2010 DOE Site Visit 37Bruce SchummBaBar
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
2010 DOE Site Visit 38Bruce SchummBaBar
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
2010 DOE Site Visit 39Bruce SchummBaBar
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