doe site visit thursday, june 18, 2009 bruce a. schumm santa cruz institute for particle physics...
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![Page 1: DOE SITE VISIT Thursday, June 18, 2009 Bruce A. Schumm Santa Cruz Institute for Particle Physics University of California, Santa Cruz BaBar](https://reader033.vdocuments.site/reader033/viewer/2022050714/56649d425503460f94a1cc6b/html5/thumbnails/1.jpg)
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
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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)
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2009 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 →(ρ,ω)“Exclusive” approach
B→Xd “Semi-Inclusive” approach
CP Violation in B →ρo
Conclusions
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2009 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)
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2009 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 →(ρ,ω)(“Standard” Approach)
B→Xd (“Semi-Inclusive” Approach)
Status of |Vtd/Vts|
CP Violation in B00
Conclusions
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2009 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)
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2009 DOE Site Visit 7Bruce SchummBaBar
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
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2009 DOE Site Visit 8Bruce SchummBaBar
B Factory Data SetsB Factory Data Sets
700 fb-1
440 fb-1
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2009 DOE Site Visit 9Bruce 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
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2009 DOE Site Visit 10Bruce 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
• After event selection, S/B is roughly 1:1
• Continuum measured from below-peak running
• B/Bbar backgrounds must be identified and constrained
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2009 DOE Site Visit 11Bruce 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)
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2009 DOE Site Visit 12Bruce 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 expected by end of year
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2009 DOE Site Visit 13Bruce SchummBaBar
OutlineOutline
Effective Neutral Currents: General Motivation
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
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2009 DOE Site Visit 14Bruce 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
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2009 DOE Site Visit 15Bruce 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
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2009 DOE Site Visit 16Bruce 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
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2009 DOE Site Visit 17Bruce SchummBaBar
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
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2009 DOE Site Visit 18Bruce SchummBaBar
|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)
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2009 DOE Site Visit 19Bruce 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)]
“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)
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2009 DOE Site Visit 20Bruce SchummBaBar
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
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2009 DOE Site Visit 21Bruce 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 < 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
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2009 DOE Site Visit 22Bruce SchummBaBar
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
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2009 DOE Site Visit 23Bruce SchummBaBar
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?
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2009 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:
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2009 DOE Site Visit 25Bruce SchummBaBar
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
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2009 DOE Site Visit 26Bruce SchummBaBar
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
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2009 DOE Site Visit 27Bruce SchummBaBar
Backup Slides
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2009 DOE Site Visit 28Bruce 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)
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2009 DOE Site Visit 29Bruce 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
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2009 DOE Site Visit 30Bruce 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
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2009 DOE Site Visit 31Bruce 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