overview of the cleo experiment d and d s leptonic decays to and :
DESCRIPTION
Leptonic Charm Decays at CLEO. Overview of the CLEO experiment D and D S leptonic decays to and : Measurements of absolute branching fractions Measurements of absolute decay constants Comparison with theory (LQCD). Victor Pavlunin on behalf of the CLEO collaboration - PowerPoint PPT PresentationTRANSCRIPT
Oct., 2006 1
Overview of the CLEO experiment D and DS leptonic decays to and :
Measurements of absolute branching fractions Measurements of absolute decay constants
Comparison with theory (LQCD)
Victor Pavlunin on behalf of
the CLEO collaborationDPF-2006
Oct., 2006 2
The CLEO detector
The CLEO detector was developed for B physics at the Y(4S). CLEO-III configuration:
B-field: 1.5 T Gas (drift chamber): He and C3H8
Tracking: 93% of 4, P/P0.6% for a 1.0 GeV track Hadron particle ID: RICH (80% of 4) and dE/dx E/M crystal calorimeter: 93% of 4π, E/E 2.0%
(4.0)% for a 1.0 GeV (100 MeV) photon Muon prop. chambers at 3, 5 and 7 I .
Transition from CLEO III to CLEO-c:
B-field: 1.5 T 1.0 T Silicon vertex detector low mass stereo drift
chamber
Advantages of running at the (3770) for charm physics:
Pure DD, no additional particles [DD at (3770)] = 6.4 nb [(cc) at Y(4S) ~1.3 nb] Low mulitplicity, high tagging efficiency (>20%)
An event taken at the
Y(4S)
KDKD
DDee
,
,)3770(
6-layer all-stereo
Oct., 2006 3
The main task of the CLEO-c open charm program:
Calibrate and Validate Lattice QCD
Help heavy flavor physics constrain the CKM matrix now: Precision tests of the Standard Model or Discovery of new physics beyond the SM in b or c quark decays
Difficulty: hadronic uncertainties complicate the interpretation of exp. results:
Help LHC search for and interpret new physics if new physics is strongly coupled in the future
Why a Charm Factory?
Reduce theory error on B form factors and B decay constants using tested
LQCD
Oct., 2006 4
Leptonic decays (D+ and Ds):
Semileptonic decays (D e, D Ke ):
Combination of leptonic and semileptonic decays:
Examples of LQCD tests and their impact
Bd Bd2*2 || tbtdB VVfRate
d
2)(
2 ||)( scdD VfRate
s
LQCDExperimentKnown to 1% from
the CKM unitarity
Lattice predicts fB/fD and
fB/fBs with small errors
precise fD gives precise fB
and |Vtd|; fD/fDs checks fB/fBs and allows precise |Vtd|/|Vts|
|VCKM|2
|fD|2
D
|f(q2)|2
|VCKM|2
D )(
,)(22
222
)(
eMqwhereqfVRate scd
Test LCQD calculations of f+
(q2) in the D system and apply them to the B system for |Vub| and |Vcb|
The topic of the next CLEO talk
222 /)()(/)( DfqfDeD Test LQCD with no errors from CKM couplings
)(K
The main topic of this talk
Oct., 2006 5
CLEO-c Data SamplesResults presented in this talk were obtained using the
following data samples:
(3770): total luminosity = ~ 280 pb 1
ECM = 4170 MeV: total luminosity = ~ 200 pb1
CLEO scanned ECM = 3.97 – 4.26 GeV:
Optimal energy for Ds physics:
ECM = 4.170 GeV
Dominant production mechanism:
[Additional 120 pb-1 at ECM = 4170 MeV already collected: to be analyzed]
*SS DDee
*SS DD
SS DD**SS DD
DATA
Preliminary
Oct., 2006 6
D(s) Leptonic Decays
cdV
Df
222
2222 ||)1(
8
1)( cd
D
lDlDF V
M
mMmfGlD
Standard Model predicts: D decays: Ds decays:
Use Vcd and Vcs to extract fD and fDs, and compare them to theory
7.2:0.1:103.2)(:)(:)( 5 e
7.9:0.1:105.2)(:)(:)( 5 e
Oct., 2006 7
D+ and D+ at the (3770)
References:PRL 95, 25801 (2005)PRD 73, 112005 (2006)
Oct., 2006 8
Tagging at the (3770) The (3770) is about 40 MeV above the DD pair threshold (
)
Variables used in the tag reconstruction:
Leptonic decays are identified using missing mass squared:
DD PP
22candidatebeambc PEM
beamcandidate EEE
Tagging creates a beam of D mesons with known momentum
222 )()( ppEEMM tagbeam
Oct., 2006 9
D Tags
][22 GeVPEM candidatebeambc
DATA (280/pb) All 6 modes
Cut on E and fit MBC:
Total number of tags: [158.4 0.5 (stat)]103
][22 GeVPEM candidatebeambc
K 0 K
SK SK
0 SK KK
DATA (280/pb)
Oct., 2006 10
][)()( 2222 GeVppEEMM tagbeam
D
0KD
D+ + and e+ Full event reconstruction:
require a tag, require a muon cand. (ECC
track < 300 MeV),
veto events with extra tracks and energy clusters > 250 MeV.
Results: 50 D+ candidates Estimated bckg: 2.8 events
The same analysis is repeated for D+ e+. No signal candidates are seen:
410)](1.0)(7.04.4[)( syststatDB
MeVsyststatfD
)](3)(17223[
)%90(104.2)( 5 CLateDB
DATA
Oct., 2006 11
Case I: ECCtrack
< 300 MeV
Case II: ECCtrack
> 300 MeV
Sign. Candidates: 12Est. Background: 6.1
Sign. Candidates: 8Est. Background: 5.0
D+ + Reconstruct D++ with ++ [B(++ ) ~11%]; the same
technique but two ’s complicate the analysis:
Consider two cases: Case I: ECC
track < 300 MeV ( and )
Case II: ECCtrack > 300 MeV (mostly )
No significant signal
)(: DMC
Broad MM2
)%90(101.2)( 3 CLatDB )]%90(10)2.01.1()(:[ 3 CLatDBSM
DATA
DATA
Oct., 2006 12
DS and DS at ECM = 4170 MeV
References:CLEO CONF 06-17hep-ex/0610026
Oct., 2006 13
][)( GeVDM S
KKKKS
0** KK
DS Tags (1)
Recall at ECM = 4170 MeV:
DS* decays to DS via emission of ~150 MeV
photon ~95% of the time significant smearing of MBC
Tag modes used in the analysis:Yields from M(Ds)
Total number of tags from M(Ds): [19.2 0.3 (stat)]103
*SS DDee
DATA (200/pb)
Oct., 2006 14
DS Tags (2)
To fully reconstruct the event, the photon must be detected. The missing mass squared can be used to obtain the number of tags:
22
2*
)()( ppEEEMM
SS DDCM
All 8 Modes DATA
][ 22* GeVMMTotal number of tags in the signal
region of MM*2: [11.9 0.4 (stat) 0.5
(syst)]103
Oct., 2006 15
Electron Sample
ECCtrack < 300MeV
64 events
24 events
12 events
Case I:
Case IIECC
track > 300MeV
Case III
Mostly DS +
Mostly DS +
Signal region
region
A
region
B
DATA
DATA
DS + and +(+) (1)
Full event reconstruction: Require a tag and a from DS
*, Require one additional track, Veto events with ECC > 300 MeV
or extra tracks.
Use MM2 to separate +, +(+) and background:
Consider three cases: Case I: ECC
track < 300 MeV (accept 99% of muons and 60% of pions) Case II: ECC
track > 300 MeV (accept 1% of muons and 40% of pions) Case III: require an electron
[Kinematical constraints are used to improve resolution and remove multiple combinations]
22)(
2 )()( pppEEEEMMSS DDCM
Oct., 2006 16
100 events
Sum of Case I and Case II
K0+
signal line shape
Consistency Check
Note the scale limits: 0.20 and 0.80 GeV2
MM2 MM2
MC MC+ +
DATA
DS + and +(+) (2)
Oct., 2006 17
Electron Sample
ECCtrack < 300MeV
64 events
24 events
12 events
Case I:
Case IIECC
track > 300MeV
Case III
Mostly DS +
Mostly DS +
Signal region
region
A
region
B
DATA
DATA
DS + and +(+) (3)
DS + (Case I, Reg.A) 64 signal candidates, 2.0 bkg
events:
DS + (Case I,Reg.B+Case II)
36 signal candidates, 4.8 bkg events:
Use the SM B(+)/B(+) to average results above:
DS e+ (Case III): No signal candidates:
)]%(03.0)(09.066.0[)( syststatDB S
)]%(3.0)(4.11.7[)( syststatDB S
)]%(03.0)(08.066.0[)( syststatDB S )%]19.061.0()(:06[ SDBPDG
4101.3)( eDB S
)%]5.14.6()(:06[ SDBPDG
MeVsyststatfSD )](7)(16282[
Preliminary
Oct., 2006 18
DS +(e+ )
Complimentary analysis: DS
+ with +e+ .
B(DS+)B(+e+)~1.3% is large [cf. B(DS
+→Xe+)~8%] Analysis Technique:
Find e+ and DS tag ( from DS
* is not reconstructed, same tag modes)
Veto events with extra tracks Extra energy in CC < 400 MeV
Results:
400 MeV
Xe+
)]%(5.0)(8.03.6[)( syststatDB S )%]5.14.6()(:06[ SDBPDG
MeVsyststatfSD )](12)(17278[
Preliminary
Oct., 2006 19
Comparison with theorySummary of CLEO-c results:
Unquenched LQCD [PRL 95, 122002 (2005)]
MeVsyststatfD
)](3)(17223[
MeVsyststatfSD )](6)(12280[ [Weighted average; syst. errors
are mostly uncorrelated]
11.026.1 D
D
f
fS
MeVsyststatfD
)](17)(3201[
MeVsyststatfSD )](16)(3249[
07.024.1 D
D
f
fS
CLEO-c: statistically limited
LQCD: systematically limited
An example of theor. preditions:
Preliminary
Oct., 2006 20
Conclusions An important task of CLEO-c is to calibrate and validate LQCD.
Charm leptonic decays provide particularly stringent tests.
Current precision of CLEO-c and LQCD results is comparable. CLEO-c results are statistically limited; LQCD results are limited by systematic uncertainties.
Expect a three fold increase in the size of CLEO-c data sample and a complete suite of leptonic and semileptonic measurements in the next few years.
On a longer time scale, BES III (China) should be able to improve CLEO-c results and further constrain the theory.
Oct., 2006 21
Additional Slides
Oct., 2006 22
)3770(
Data taking started in the fall of 2003
Note
: Log
Scale
Over 20 years operated at the Y(4S)
~16 fb-1 at the Y(4S)
CESR and CLEO
The CLEO experiment is located at the Cornell Electron Storage Ring (CESR), a symmetric e+e-
collider that operated in the region of the Upsilon resonances for over 20 years:
Max inst luminosity achieved: 1.31033 cm-2s-1
Total integrated luminosity at the Y(4S): 16 fb-1
Lots of important discoveries, e.g., Y(nS), bs, buW.
In 2003, CLEO started running at the (3770), ~40 MeV above DD production threshold, and slightly higher energies for DS studies.
Transition from CESR to CESR-c:
12 wigglers are installed to increase synchrotron radiation/beam cooling
Max luminosity achieved: ~71031 cm-2s-1
Oct., 2006 23
The main task of the CLEO-c open charm program: Calibrate and Validate Lattice QCD
Help heavy flavor physics constrain the CKM matrix now: Precision tests of the Standard Model or Discovery of new physics beyond the SM in b or c quark decays
Difficulty: hadronic uncertainties complicate interpretation of exp. results
Help LHC search for and interpret new physics (future)
Why a Charm Factory?
Reduce theory error on B
form factors and B decay constants
using tested LQCD
A realistic example using recent CKM status (new Bs mixing results are not included):
200 fb-1
at Babar/Belle 500 fb-1 at Babar/Belle
Oct., 2006 24
Why now?
C. Davies opened her talk in Lisbon at EPS-2005: “There has been a revolution in LQCD…”
BEFOREquenched
NOWunquenchedPRL 92, 022001 (2004)
LQCD demonstrated that it can reproduce a wide range of mass differences and decay constants in unquenched calculations. These were postdictions.
Testable predictions are now being made for:
Decay constants fD and fB; D and B Semileptonic form factors
.exp
LQCD
.exp
LQCDCLEO-c can test fD and D semileptonic form factors
Oct., 2006 25
Tagging at the (3770)
The (3770) is about 40 MeV above the DD pair threshold ( )
One of the two D’s is reconstructed in a hadronic “tag” mode (e.g., K+ - ). Two key variables:
From the remaining tracks and showers the semileptonic decay is reconstructed (e.g., Ke+)
U Emiss |Pmiss| is used to identify signal, where Emiss and Pmiss are the missing energy and momentum approximating the neutrino E and P. The signal peaks at zero in U.
Full event reconstruction allows to measure any kinematic variable with no ambiguities and with high precision
DD PP
22candidatebeambc PEM
beamcandidate EEE
K-
-
e+
K+
(3770)D0 D0
D0K+-, D0K-e+
Oct., 2006 26
DS Tags at 4170
MC:DS
][GeVM BC
*SS DDee