semileptonic charm decays
DESCRIPTION
Semileptonic Charm Decays. Will E. Johns (for the FOCUS Collaboration) Vanderbilt University, BEACH 2004, July 1. Subjects Covered. Published Results. Coming Soon. Works in Progress. Data from 96-97 run of FOCUS. -Vertex Resolution -Particle ID -Mass Resolution. Lots of Pubs. - PowerPoint PPT PresentationTRANSCRIPT
Semileptonic Charm Decays
Will E. Johns (for the FOCUS Collaboration)
Vanderbilt University,BEACH 2004, July 1
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Factors) Form(,
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00
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0*
KD
DKD
D
KD
KD
KD
KD
DKD
D
D
KD
KD
KD
S
S
S
S
Subjects Covered
Data from 96-97 run of FOCUS
Over 1,000,000Reco’d. Charm
-Vertex Resolution-Particle ID-Mass Resolution
VeryGood
Lots ofPubs
Semileptonic Charm Decays
022
222
2
cossin4
sin})cos1()cos1{(
coscos
V
V
V ddd
(D decay, No form factors, V decays to spin 0 particles)
Neutrino is left handed
Prefers W spin along muon,e
V products spinless
Prefer LZ=0
Form Factors
Scalar Resonance? CP?
More than just CKM measurement tools…
FOCUS saw discrepancies in the data
2
20
2
2
2
5
)(sincos2
)()cos1(sin
)()cos1(sin
coscos
0*
0*
0*
qHB
qHBe
qHBe
ddddqdmd
KV
Ki
V
Ki
V
Vk
Phys.Lett.B535:43-51, 2002hep-ex/0203031
0*KD
Yield 31,254
DataMC
Focus “K*” signal
matches model
-15% F-B asymmetry!
FOCUS added a term, things got better
2
20
2
2
2
5
)()(cossin2
)(sin)cos1(
)(sin)cos1(
coscos
0*
0*
0*
qHAeB
qHBe
qHBe
ddddqdmd
iKV
Ki
V
Ki
V
Vk
L=0 ansatz
Signal Events weightedby avg(cosV):
No added term
FOCUS Semileptonic cuts description ),( KDLook for N bodies with a muon
L/ – Lp
s ISO1 – CL DK’s in prim
DCL – CL of DK vertex
MuCL – CL for Muon ID Cuts on P( for ’s
Cerenkov for ’s and K’s (from ~ 4-60 GeV/c)
Vertexing cuts:
ISO2 – No Xtra trks in DK OOM – No DK’s in stuff
Particle ID cuts: TRKFITcl – Muon P consistency
MISIDMCS Radius, Decay Prob
(Ask me offline for all the detailed cut values!)
FOCUS Form Factors
and ,parameters waveS and)0()0(
)0()0( Fit to
)/1.2(,/1)0()()/5.2(,
/1)0()(
)(4)())((2
1)(
0set factor, has )()(2)()()(
1
22
1
222
2222
2
22
222
1222
2
20
22221
2
AAAr
AVr
cGeVMMq
VqVcGeVMMq
AqA
qAmMKMqAmMqmM
qmqH
mqHqVmMKMqAmMqH
v
VV
AA
ii
KD
DKDKD
K
tKD
DKD
Tried in fit,no sensitivity (E791?)
(common – vary generated parameters in Montecarloby using agreement with reconstructed distributions and data)
Pioneered by D.M. Schmidt for E691 K*ev analysis: NIM A 328 (1993)
0*
KD
2max
2V /in 3 and in 3 ,cosin 5 ,cosin bins 5 qq
Kmin 4 and in 3 ,cosin 3 ,cosin bins 3 V
S-wave termBreaks symmetry
S-wave term andr’s essentially decouple
FOCUS Form Factors 0*
KDCuts similar to previous, some change to get uniform acceptance, one extra
Cut on q2 < 0.2 GeV2/c2
r’s are flat, feeling mμ? Goodness of fit issue
Right sign – Wrong sign
Charm Background
Systematic ChecksS-wave – varied cuts35 fits – Sample VarianceForm Factor (3 sources)1) Varied Cuts2) Split sample
3) Vary MC input Charm Backgrounds
)/9.0(2,, cGeVKD mDDP
2)0()0(2
1
3 AA 064.0049.0875.02
039.0057.0504.1
)()(05.007.068.0
015.0022.0330.0
rr
sysstat
A
V
Phys.Lett.B544:89-96, 2002hep-ex/0207049
Very Clean Data
0*
KDForm Factors Comparison
S-Wave effects apparent only with high statistics
Lattice Gauge!
Experiment Models
A more detailed look at the K line shapeTake advantage of the very clean signal
Previous best K* parametersLass (1988) K scattering
Spectra is complicated
Mass range limit in fitMore Blatt-Weisskopf radius info away from pole
FOCUS sees S-wave effects primarily Below K*
Using LASS parametersfor ER model of
Constant
FOCUS PRELIMINARY
K* MassK* WidthBL-WK radius#K* eventsScalar Fraction
Mass and WidthDon’t change
-Careful studies of resolution effects too
FOCUS PRELIMINARY200051.0
00022.0*
200015.000016.0*
/00081.004751.0
/00030.089463.0
cGeV
cGeVM
K
K
Systematics by varying cuts, background contribution, shapes
FOCUS Form Factors SD- Event by Event version of discrete transform method
)()(284.0202.0713.020148.0250.0549.1
sysstatrrV
- No evidence for S - wave
Phys.Lett.B586:183-190, 2004hep-ex/0401001
- Backgrounds higher (cut on M
Ds form factor enigma
Theoretically the Dslform factor should be within 10% of D+ K*l The rV values were consistent but r2 for Dslwas 2 higher than D+ K*l
E79
1C
LEO
E65
3
E68
7
BK
S
LMM
S
ISG
W2
0
0.5
1
1.5
2
2.5
3R
V
0
0.5
1
1.5
2
2.5
3
R2
circa 1999
ISG
W2
Focu
s
E79
1C
LEO
E65
3
E68
7 BK
S
LMM
S
0.0
0.5
1.0
1.5
2.0
2.5
3.0
0 1 2 3 4 5 6 7 8 9
RV
But the (2004) FOCUS measurement has consistent r2 values as well!
Ds versus D+ K*l
Backgrounds Make a difference! 0D
Biggest Players:Signal, ~400 events (red and dots)Combinatoric Background,~750 events (pink hatch)Muon Misid, ~300 events(faint black histogram)
A peek at:
Search for Cabibbo Suppressed Ds semileptonic decay
c
ss
d
W
u u
K
cdV
Cabibbo suppressed SL Decay
*K
sD
Would be a discovery!
A Cabibbo favored SL decay
s
sc
s
W
csV
u u
K
K sD
Easy to see and study
Right SignWrong Sign
MK (GeV/c2)
DsK*decay is a small WS background component in our previous D+K*work
Note kaon and muon have same sign
K+ K- mass in KK events K mass in K events
What’s this?
Preliminary results of the search
dataMC
After lots of cuts
In the loosely cut sample, the MC was a poor match to the observed WS Kspectrum. Large non-charm contribution?
With tight cuts, the MC matched the data away from the K* peak. We saw a excess in K* yield in data over MC
*
12.9 3.3 ??? %s
s
D K
D
We compared the WS K spectrum to a MC that incorporated all known charm decay and normalize the MC to the D+K*yield observed in the data
If this K* excess were interpreted as DsK*, we would obtain...
MK (GeV/c2) MK (GeV/c2)
This BR is very consistent with (10 ±1.3)% predicted by R.J. Oakes et al. (1997) (hep-ph/9708277)
FOCUS BR Measurements
even
ts /
5 M
eV/c
2
)(
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S
S
D
D
KD
KD
)! cuts(
/18.0}){(}){(0*
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DD
cGeVKMKM
KD0*
KD
SDSD
Includes S-wave interference
)(048.0)(033.054.0)(
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sysstatD
D
S
S
(1.5) 2.2,e)(quadratur Total(0.94) 1.57, ff) (Bk,fit Vary
(1.12) 1.57, Samples Splitting(1.06) 0.71, CutsVary
:)( for
offraction a as expressed:errors Systematic
stat
SDD
Phys.Lett.B540:25-32, 2002hep-ex/0206013
)(021.0)(010.0602.0)(
)(0*
sysstatKD
KD
even
ts /
10 M
eV/c
2
BR Comparisons to Exp. & Models
focus
cleo2
cleo
argus
e687
0.2
0.4
0.6
0.8
0.540 0.040
BR relative to are consistent
K
*l
/K
E691
E653
Focus
Argus
Omega
Cleo 1
Cleo 2
Cleo 2
E687
0.3
0.4
0.5
0.6
0.7
0.8
0.9
muons electrons
0.620.02
BR relative to K …not so good
What about
0
0*
KD
KD?
-Could resolve lepton ID issues- Topological trouble though > need an extra particle for K*-Most Experiments measure ~0.5 (E687 too!) (some use rates though…compare D+ D0)
10
0*
KD
KDBut CLEO2 Reported )( 0 KDBUsing the
From the PDG
nsDD eKeK /)7.925()()( 00
But using PDG values we also find: Isospin Violation?
0
0*
KD
KDFOCUS
In the FOCUS silicon)(&)( 0*0 KKKS
Reconstruct both
Drawback: Only about 10% of Ks>+-
Decays occur in the FOCUS silicon
Find Background Dominated by D>KsX
FOCUS is world’s best
0
0*
KD
KD
034.0045.0625.00
KD
KD
nsDD KK /)1111()()( 00
Correct for S-Wave:
hep-ex/0406060Submitted to PLB
030.0043.0594.00
0*
KD
KD
Measure:
Use Focus K* and PDG Kcompare to D0: Isospin OK again
11.072.00
0
KD
eKD?=1.03=? 07.012.10
0
KD
eKDLong standing “difference” for D0 is in “wrong” direction
Other Exp’s Models
Comparison to other Experiments and Theory
Focus measurementssuggest little “missing”Semileptonic rate
%9.12.17)( anythingeDPDG
%9.12
))2/3((6.14.1
0
eKKDSum of PDG CA e modes
Focus ’s as e’s
%2.19.14))03.1()05.1(( 0
KKD
Hard to believe PDG forPS electron is correct
Preview of other FOCUS analysis
)( 00SKD 0D KD0
-Plot of pseudo D*-D mass difference-Will repeat Vector analysis (tough to see S-wave)-measure q2 shape and BR for and K (expect BR/BR<10%)
Conclusions:
• Resolved some outstanding enigmas ( ff’s, V/PS Ratio, PDG rates)
• Raised some new ones (low q2 in K*, proper S-wave description
• We’ve gotten a lot of physics out of the careful analysis of the Vector decays (S-wave, B(K*,f), M(K*), r’s, W(K*), CS(K*)…
• Looking at new things