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Experimental Prospects for CP and T Violation Studies in Charm. Giampiero Mancinelli University of Cincinnati CHARM 2007 – Cornell, USA. Outline. BESIII. CLEO-c. E-791. SUPER-KEK. THE RESEARCH CP Violation in the Charm Sector Direct CP Violation Experimental Techniques - PowerPoint PPT Presentation
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Wol
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Giampiero MancinelliUniversity of Cincinnati
CHARM 2007 – Cornell, USA
Experimental Prospects for Experimental Prospects for CP and T Violation CP and T Violation Studies in CharmStudies in Charm
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OutlineTHE RESEARCH
CP Violation in the Charm Sector
Direct CP Violation
Experimental Techniques
CP/T Violation Searches
Charged D decaysNeutral D decays
CP states3-Body
CP Violation at the (3770)T-odd Correlations
Summary: Current Status
Future Prospects
Conclusions
THE PLAYERS
CLEO-c BESIII
E-791
SUPER-KEK
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Charming CP Violation Sakharov conditions for baryogenesis (1967):
Baryon number violationCP violation Non-equilibrium
SM CP Violation in kaon and beauty systems too smallNeed other sources
Three types of CP ViolationCPV in mixing matrix (tiny)
CPV in decay amplitudes
CPV in interference between mixing and direct decay, for a subset of final states (mixing suppressed, hence very small)
fDAfDA
122
1212
1212
22
iMiM
qpRm
f
fim
f
ff A
AeR
AA
pq
See previous sessionfor CPV in mixing
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Direct CP Violation in Decay
Two amplitudes with different strong & weak phases needed to observe CPV (in SM from tree and penguins)
THE DECAYS
Cabibbo Favored (CF)
Singly Cabibbo Suppressed (SCS)
Doubly Cabibbo Suppressed (DCS)
c sdu
c dduc ssu
c dsu
1 32 2 *
1 2 1 2 1
2 21
2
*2Im ( )( ) ( ) 10( ) ( ) 2Re ( )
CPsinf f
Af f A A A A co
A A
s
strong phase difference
c
s
uW+
uW+
c
s
ss
e.g. SCS D0 → K+K-
K+
K-
K-
K+
uD0
D0
2 weak amplitudes with phase difference
u
u
u
s
Only SCS decays probe penguins
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CP Violation in the Standard ModelStandard Model charm physics is “CP conserving”
2x2 Cabibbo quark mixing matrix is real (no CPV at tree level)CPV in penguins and loops (by virtual b quarks)
Diluted weak phases in SCS decaysIn mixing, CPV enters at O(VcbVub/VcsVus)In decay, penguin CPV enters at O(VcbVub/VcsVuss/)
No weak phases in CF and DCS decays …except D+ K0+ - SM ~0.003 (CPV in K0 decay)
Note: in general we can separate direct and indirect CP Violation by:
Combine measured ACP with time-dependent CPV measurements (both for CP eigenstates)Just using time-integrated measurements (assuming negligible new CPV in CF or DCS decays):
The time-integrated CP asymmetry for CF decay to a CP eigenstate gives indirect ACP
e.g: ACP_DIRECT(P+P−) = ACP(P+P−) − ACP(KS00) , P = K,
Light readings:New physics and CP violation in singly Cabibbo suppressed D decays. Y. Grossman, A. L. Kagan, Y. Nir, Phys.Rev.D75:036008,2007. “I Know She Invented Fire, But What Has She Done Recently?" - On The Future Of Charm Physics, I.I. Bigi, Int.J.Mod.Phys.A21:5404-5415,2006. Mixing and CP-violation in charm. A. A. Petrov, Nucl.Phys.Proc.Suppl.142:333-339,2005. A Cicerone for the Physics of Charm, S. Bianco, F. L. Fabbri, D. Benson, I. Bigi, Riv. Nuovo Cim. 26N7 (2003) 1.
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CP Violation and New Physics (NP)Extensions of the Standard Model (ex: SUSY) contain CP violating couplings that should show up at some level (1%?) in flavor physics
Precision measurements and theory are required to detect the NP
BSM Physics: charm is unique probe of the up type quark sector, especially models in which CKM mixing is generated in the up sector
top quarks: do not hadronize No T0-T0 oscillationsHadronization helps observability of CP Violation
up quarks : 0, η and η′ do not decay weaklyNo 0-0 oscillations possible CP asymmetries mostly excluded by CPT theorem)
(relatively) Large statistics
Flavor models where the CKM mixing is “generated” in the up sector predict large D − D mixing and sizable CPV in D, but smaller effects in the B sector
SCS D decays are now more sensitive to gluonic penguin amplitudes than are charmless B decays
CF and DCS decays: Direct CPV in charm would
mean NPSCS decays:
SM ~ 10-3 from CKM matrix
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Experimental Approaches for DCPV Measure asymmetry in time integrated partial widths Measure asymmetries in final state distributions on Dalitz plots
Exploit quantum coherence of DD produced in (3770) decays
Study T-violation in 4-body decays of D mesons (assuming CPT) with triple product correlations (T-odd)
All analyses (except CLEO-c) share many common featuresMany D0s produced in colliders,
Easy to determine the flavor of the D0 (by unbiased tag: D*
D0)Common backgrounds (e.g. K)
Random combining with a real D0K+-
Multibody D0 decay from D*D0 Random Kcombinatoral background
Signal and Background yields taken from mKvs M(D*-D0)Signal shape/resolution functions/efficiency calibrations taken from CF modesp(D*) cut to suppress from BD*D decaysOften normalize asymmetries to CF (or other) modes
Keep many systematics to a minimum
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BABARK−K++ K+K--
+ -
K*0K+ K*0K-
K−K++ K+K--
~42500 events80fb-1
D+ → K−K++, -++
~55000 events80pb-1
193 pb-1
D+ → K−K++ D+ → -++
CDFII
Large statistics gives access to detailed features in Dalitz plots
http://www-cdf.fnal.gov/physics/new/bottom/040422.dplus/
Phys. Rev. D71, 091101 (2005)m(-++)
m2(-+)m
2 (-+
)
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D0KYield: 180K
123 pb-1
D0 KK, - ISM CPV~10-3 in single Cabibbo suppressed modes (KK,), but null in Cabibbo allowed (K)
BR(D0->KK) >> BR(D0->) (R~2.8) – Large FSI and/or penguin contributions
NP CP asymmetriesStandard Model (Buccella et al, 1995) KK: (0.01 ± 0.08)%,
: (0.002 ± 0.001)%CDF II
Use D0K as normalization mode D0KKYield: 16220 200
D0Yield: 7334 97
Issues:Tracking charge asymmetrypartially reconstructed D background for KK modePhys. Rev. Lett. 94, 122001 (2005)
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BABARAnalysis Difficulties:
Precise quantification of asymmetry in D0 flavor taggingForward-backward asymmetries in cc production (novel issue)
Interference in e−e+ -> cc as mediated by either a virtual photon or a virtual Z0.
Higher-order QED box- and Bremsstrahlung-diagram interference effects
Can produce asymmetries due to boost of the CMS relative to the lab at asymmetric BABAR
Data corrected for charge-dependent detection efficiencies By tagging with an independent sample of D0 decays
Systematics:All corrections used for data will be calculated from data.
Goal: reduce systematics in these measurements to the 0.1% level
Soft-Pion Tagging efficiency corrections calculated from the CF decay (K)
With 400 fb-1 we expect:
KK (ACP)= ~ 0.3 10-2 (stat.) (ACP )= ~ 0.5 10-2 (stat.)
Both results expected to be statistically dominated
D0 KK, - II
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CLEO-c’s MeasurementsNew!
281 pb-1At the (3770)
Pure DD final state, no additional particles Low particle multiplicity(DD) = 6.4 nb ((4S)BB ~ 1 nb)Single tag sample
Mostly CF modesHigh efficiencies
SCS
Uncertainties ~1% most casesCharged Kaon tracking largest syst. ~0.7%
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Why Dalitz Plot Analyses?In case of indirect CPV and final CP eigenstates the time integrated and time dependent CP asymmetries are:
Universal
Equal to each other
In contrast, for direct CPV:
The time-integrated asymmetries are not expected to be universal
Parts of phase-space might have different asymmetries
They may even cancel each other out when integrated over the whole phase-space
New Physics might not show up in the decay rates asymmetries
It could show up simply in the phase difference between amplitudes!
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3-Body Dalitz Plot Analyses - I3-Body decays permit the measurement of phase differences
The Dalitz plot technique allows:
Increased sensitivity to CP asymmetry
Probes the decay amplitude rather than the decay rate.
Access to both CP eigenstates (e.g. D00, f00, 00, …) and non eigenstates (e.g. D0+--+, K*+-K-+, …) with relatively high statistics in the modes D0-+0, D0K-K+0, …
As measurements are normalized to the whole phase space, the flavor dependence of s tagging efficiency is null and the effect of mistagging is very small.
CLEO
D0-+0 - Difference in the integrated coherent sum of all amplitudes across the Dalitz Plot between D0 and D0 events
D0KS-+ - Full Dalitz analysis (see next slide)
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3-Body Dalitz Plot Analyses - IIBABAR (expect results this Fall)
D0-+0, D0K-K+0
MODEL DEPENDENT approach: fit D0 and D0 Dalitz plots separately, with a resonance (isobar) model (higher systematic uncertainties)
Parameterize the amplitude coefficients explicitly in the form: A eiδ = a ei(α + β) (1 + b/a) (for D0) A' eiδ' = a ei(α - β) (1 - b/a)
(for D0) Calculate |b| / |a|, values, asymmetries
in the fit fractions for each isobar.
Follows CLEO’s KS analysis technique, (Phys.Rev.D70:091101,2004).
MODEL INDEPENDENT approach: use moments of the cosine of the helicity angle for each of the three channels ( h-h+, h-0, h+ 0); plot vs invariant mass.
Measure asymmetry in these moments.
The phase/interference information is (mostly) contained in the odd moments
Decay rate asymmetry is contained in the even moments.
D0→ρ0π0 b=-0.05 = -5o
D0→ρ0π0 b=0 =0
D0-+0
MC
MC
m2(-+)
m2(-+)m
2 (-+
)m
2 (-+
)
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(3770): Quantum Correlation Analysis - I
Pure JPC = 1-- initial state CP+
If a D0 (tag) decays to a CP eigenstate f1, CP conservation requires the recoiling state f2 to have a definite CP as well, which must be of opposite sign:
e+e- (3770) D0D0
e+ e
0D
0D
+
K+
Quantum Correlation Analysis (TQCA): Due to quantum correlation between D0 and D0, not all final states allowed.
CP(f1 f2) = CP(f1) CP(f2) (-1)l = CP+
- - (since l = 1) e.g. K+K- DCP ’’(3770) DCP Ks0 (-1) l
+ - - = CP+
At the (3770) (CLEO-c)22% double tagging efficiency (~0.1% @ (4S))
Same number of DD fully reconstructed as BB @ (4S)
Unique CPV search strategyComplementary to other experiments
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K-+ vs K-+
K-+ vs K+-
CP+ vs CP+
CP- vs CP-
K vs CP+
K vs CP-
CP+ vs CP-
(3770): Quantum Correlation Analysis - II
Reconstruct both D mesons (double tag)
Maximal constructive interference
Forbidden by CP
Conservation
Data favors QC interpretation: constructive and destructive interference and no D mixing
CP+ CP+
CP- CP-
CP+ CP-
K K
K K
K CP±
CP± K
X Kl
Interference of Cabibbo Favored with
Doubly Cabibbo SuppressedUnaffected
Forbidden (Bose Symm., if no D
mixing
<KD0>/<KD0> = rei
New!
Data consistent with no C+ initial state,(~1.5%, stat dominated) “hence” no CPV
Improved technique + KL CP+ modes
Interference: Two paths to K-+ vs K+-
281 pb-1
cos = 1.06 0.19 0.06
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T Violation: T-odd Correlations
Some references:E. Golowich and G. Valencia, Phys. Rev. D 40, 112 (1989)I.I. Bigi, Proceedings of KAON2001, 417 (2001)(*) I.I. Bigi, A.I. Sanda,‘CP Violation’, Cambridge University Press 2000
We can build T-odd asymmetries as:
And the T-Violation asymmetry as:
tests T-Violation even with strong phases
0 00 00 0 0 0
T TT TT T
T T T T
C CC CA A
C C C C
12T Viol T TA A A
Method searches for Triple Product Asymmetries in (e.g.) D0 → K−K+−+
T-odd correlations can be formed using the momenta of the decay products (and assuming validity of the CPT theorem):
Under time reversal T, CT →−CT .CT<>0 does not necessarily established T-Violation, because FSI can “fake” this asymmetry(*)
Consider D0 → K+K-+-
where we can compute:
Finding:
establishes T violation.
T KC p p p
T KC p p p
T TC C
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T-Violation Measurements
FOCUSFOCUSYield: 828
370 fb-1Yield: ~32000
BABAR
Preliminary
D0 → KS0K+−+D0 → K−K+−+
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Direct CP/T Violation Results – D0 Decays
Experiment (year)
Decay mode ACP (%) Comments
CDF (2005) D0 K+ K- 2.0 1.2 0.6CLEO (2002) D0 K+ K- 0.0 2.2 0.8FOCUS (2000) D0 K+ K- - 0.1 2.2 1.5CDF (2005) D0 + - 1.0 1.3 0.6CLEO (2002) D0 + - 1.9 3.2 0.8FOCUS (2000) D0 + - 4.8 3.9 2.5CLEO (2001) D0 K0
S K0S - 23 19
CLEO (2001) D0 0 0 0.1 4.8CLEO (2001) D0 K0
S 0 0.1 1.3
CLEO (1995) D0 K0S
2.8 9.4CLEO (2005) D0 + - 0 1 (+9-7) 5 Dalitz plot –
integr.CLEO (2004) D0 K0
S + - - 0.9 2.1 (+1.6-5.7) Dalitz plot
analysisBELLE (2005) D0 K+ + - - - 1.8 4.4 A of ratios DCS/CFFOCUS (2005) D0 K+ K- + - - 8.2 5.6 4.7CLEO (2007) D0 K- + - 0.4 0.5 0.9CLEO (2007) D0 K- + 0 0.2 0.4 0.8CLEO (2007) D0 K- + + + 0.7 0.5 0.9BELLE (2005) D0 K+ - 0 - 0.6 5.3 A of ratios DCS/CFBABAR (2007) D0 K+ - - 2.1 5.2 1.5 A of ratios DCS/CFBELLE (2007) D0 K+ - 2.3 4.7 A of ratios DCS/CFFOCUS (2005) D0 K+ K- + - 1.0 5.7 3.7 T violation -
TPCor
Partiallist
New!
Ne
w!
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Direct CP/T Violation Results – D+ Decays
Experiment (year)
Decay mode ACP (%) Comments
BABAR (2005) D+ K- K+ + 1.4 1.0 0.8 A of ratios SCS/CFBABAR (2005) “ D+ + 0.2 1.5 0.6 Resonant substructure
of D+ K- K+ +BABAR (2005) “ D+ K*0 K+ 0.9 1.7 0.7CLEO (2007) D+ K- K+ + - 0.1 1.5
0.8FOCUS (2000) D+ K- K+ + 0.6 1.1 0.5 A of ratios SCS/CFE791 (1997) D+ K- K+ + - 1.4 2.9 A of ratios SCS/CFE791 (1997) “ D+ + - 2.8 3.6 Resonant substructure
of D+ K- K+ +E791 (1997) “ D+ K*0 K+ - 1.0 5.0FOCUS (2002) D+ K0
S + - 1.6 1.5 0.9
CLEO (2007) D+ K0S + - 0.6 1.0
0.3CLEO (2007) D+ K0
S + 0 0.3 0.9 0.3CLEO (2007) D+ K0
S + + - 0.1 1.1 0.6CLEO (2007) D+ K-
+ + - 0.5 0.4 0.9
CLEO (2007) D+ K- + + 0 1.0 0.9 0.9
CLEO (2007) DS+ K+ - 20 18
CLEO (2007) DS+ K+ ’ - 17 37
CLEO (2007) DS+ K0
S 27 11
CLEO (2007) DS+ K+ 2 29
E791 (1997) D+ + - + - 1.7 4.2 A of ratios SCS/CFFOCUS (2005) D+ K0
S K+ + - 2.3 6.2 2.2 T violation through triple product correlationsFOCUS (2005) DS
+ K0S K+ + - - 3.6 6.7
2.3
New! Partial
list
New!
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Average Result, by ModeDecay mode ACP (%)
D0 K+ K + 1.4 ± 1.2
D0 KS0 KS
0 2.3 ± 1.9D0 + + 1.3 ±
1.3D0 0 0 + 0.1 ±
4.8D0 + 0 + 1 ± 9D0 KS
0 + 0.1 ± 1.3
D0 K + - 0.4 ± 1.0D0 K + 0 + 0.2 ±
0.9D0 K + + - + 0.7 ±
1.0D0 K+ 0.8 0.8 ± 3.1D0 K+ 0 0.1 ± 5.2D0 KS
+ 0.9 ± 4.2D0 K+ + 1.8 ± 4.4D0 K+ K + 8.2 ± 7.3D+ KS
+ 0.9 ± 0.9D+ KS
+ 0 ++ 0.3 ±
0.9D+ KS
+ + - + 0.1 1.3
Decay mode ACP (%)D+ K-
+ + - 0.5 1.0D+ K-
+ + 0 + 1.0 1.3
D+ KS K+ + 7.1 ±
6.2D+ K+ K + + 0.6 ±
0.8D+ + + 1.7 ± 4.2D+ KS
K+ + 4.2 ± 6.8
AT
SCS modes
For most references http://hal9000.mib.infn.it/~pedrini/hfag/charm_asymcp.htmlSee the HFAG pages http://hal9000.mib.infn.it/~pedrini/hfag/charm_todd_asym.html
Partiallist
HFAG +
my averages
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Future Prospects – Current Efforts - I D0KK,
CDF yield prospects2M D* tagged D0K per 1 fb-1 ACP) ~ 10-3 is achievable with full Tevatron run (4-9 fb-1) -
at SM limitIssue will be if trigger can cope with Luminosity increase
BABAR: 1 ab-1 KK (A)~0.2% (stat) (A)~0.3% (stat)
D+ K+K-
BABAR – now (A)~0.45 (systematically dominated – (syst~0.8)) 1 ab-1 (A)~0.28% (stat) Dalitz Analysis: fit fractions and phase differences ~ 1% and
1o precisions
D0+-0 Dalitz AnalysisBABAR 200,000 signal events @ 1 ab-1 in 1 mass region.
(A) (stat) ~ 0.25 % (integrated)If the asymmetry is larger, but confined to only a part of the
phase-space or only to certain specific decay(s), or both (constructively) in amplitude phases and magnitudes, our observation potential might be higher (or lower if destructively)
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Future Prospects – Current Efforts - II
T-Odd Correlations
BABAR (KK)
now ~ 0.9-0.6% level (if systematics under control)1 ab-1 0.55-0.35%
Relevant datasets I am aware of (larger backgrounds than KK):
CLEO: D0+-+- 7,300 - D0+-00 2,700 – D++-+0 5,700 BABAR: D0+-+- - current ~140,000 – 1 ab-1 ~320,000 + many large CF decays datasets from all 3 experiments
NOTE: Expect similar yields/results from BELLE
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Future Prospects – Future Efforts
BEPCII/BESIIIData taking beginning of 2008 - 3 yrs @ 3770 = 30M DD/yr = 90M DD = ~20 times full CLEO-c dataset
Super-B (D, …)10 ab-1/yr at (4S)With option to lower energy to ~4 GeV (~1ab-1/yr)
LHCbWill implement a dedicated D* trigger stream selecting huge and clean samples of hadronic D modesIn one year of running at nominal lumi (2·1032 cm-2s-1):
Expect 250 - 500 M D* D0 decays with D0K channel = 100 times CDF !
K-K+
A < 0.08 (CLEO-c), < 0.004 (BESIII)(A) ~1 x 10-4 (stat.) LHCb/yr (A) ~6 x 10-5 (stat.) Super-B/yr
(3770) Quantum Correlation Analysis
A < 0.025 (CLEO-c) (A) ~0.01 (just KK, ) (BESIII)(A) ~7x 10-4 (stat.) Super-B/yr
KS-+ Dalitz analysis
Super-B (5 years = 50 ab-1) A < 5 10-4
BESIII – SUPER-D-too Factory (KEK and/or Frascati) – LHCb
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ConclusionsCharm physics provides unique opportunities for indirect search of NP
Theoretical calculation of x, y have large uncertainties Physics BSM hard to rule out from D0 mixing measurements alone
Observation of (large) CPV robust NP signal
SCS D decays now more sensitive to gluonic penguin amplitudes than charmless B decaysExciting new results (CLEO, Belle, BABAR): Total errors ~1% level BUT far from observation Now entering the interesting domain
Promising future: Current experiment ~0.1-0.3% in the “best” modes Future efforts (Super-Bs, LHCb, BESIII) ~ 0.001-0.01%