Transcript Document 7659591

Semileptonic
Charm Decays
Will E. Johns
(for the FOCUS Collaboration)
Vanderbilt University,
BEACH 2004, July 1
Subjects Covered
D   ( K   )   ( S - Wave )
*0
( D   K   ) ( DS    )
,




( D  K   ) ( DS    )
D   K   , DS    ( Form Factors)
*0
D   ( K   )   ( Line Shape)
( D   ( K )   )
( D   K 0   )
DS  ( K   )  
D    
D 0  K    , D 0     
D 0  ( K )  
Data from 96-97 run of FOCUS
Over 1,000,000
Reco’d. Charm
-Vertex Resolution
Lots of
Very -Particle ID
Good -Mass Resolution Pubs
Semileptonic Charm
Decays
More than just CKM measurement tools…
(D decay, No form factors,
V decays to spin 0 particles)
d 2

d cos V d cos  
Neutrino is left handed
{(1  cos   ) 2   (1  cos   ) 2  } sin 2 V


Prefers W spin along muon,e
 4 sin 2   cos 2 V 0 Prefer LZ=0
V products spinless
Scalar Resonance?
CP?
Form Factors
FOCUS saw discrepancies in the data
D   K *0  
Focus “K*” signal
Yield
Data
31,254
MC
-15% F-B
asymmetry!
Phys.Lett.B535:43-51, 2002
hep-ex/0203031
d 5

2
dmk dq d cos V d cos   d
2

i
2
 sin V (1  cos   )e BK *0 H  (q ) 


 i
2

sin

(
1

cos

)
e
B
H
(
q
)
*
0


V

K



2

2
cos

sin

B
H
(
q
)
*
0
V
 K
0




matches
model
FOCUS added a term, things got better
Signal Events weighted
by avg(cosV):
No added term
d 5

2
dmk dq d cos V d cos   d
2

i
2
 (1  cos   ) sin V e BK *0 H  (q ) 


 i
2

(
1

cos

)
sin

e
B
H
(
q
)



V
K *0 
  2 sin  (cos  B  Aei ) H (q 2 ) 

V K *0
0




L=0 ansatz
FOCUS Semileptonic cuts description
Look for N bodies with a muon
D   ( , K )  
Vertexing cuts:
ss
sp
ISO1 – CL DK’s in prim
L/s –
L
DCL – CL of DK vertex
ISO2 – No Xtra trks in DK OOM – No DK’s in stuff
Particle ID cuts:
TRKFITcl – Muon P consistency
MuCL – CL for Muon ID Cuts on P() for ’s
MISIDMCS Radius, Decay Prob
Cerenkov for ’s and K’s (from ~ 4-60 GeV/c)
(Ask me offline for all the detailed cut values!)
FOCUS Form Factors
H  (q 2 )  ( M D  mK ) A1 (q 2 )  2
H 0 (q ) 
1
2
2mK
M DK
V (q 2 )
M D  mK
*0 

D K  
H t (q 2 ) has m2 factor, set  0
 2
M D2 K 2
2
2
2
2 
(
M

m

q
)(
M

m
)
A
(
q
)

4
A
(
q
)
D
K
D
K
1
2
2 
M

m
q 
D
K

Ai (q 2 ) 
Ai (0)
, ( M A  2.5 GeV / c 2 )
2
2
1 q / M A
Fit to
rv 
V (0)
A1 (0)
r2 
A2 (0)
A1 (0)
V (q 2 ) 
Tried in fit,
no sensitivity
(E791?)
V (0)
, ( M V  2.1 GeV / c 2 )
2
2
1 q / MV
and S  wave parameters , A and 
(common – vary generated parameters in Montecarlo
by using agreement with reconstructed distributions and data)
Pioneered by D.M. Schmidt for E691 K*ev analysis: NIM A 328 (1993)
3 bins in cos V , 3 in cos , 3 in  and 4 in mK
S-wave term
Breaks symmetry
2
5 bins in cosV , 5 in cos , 3 in  and 3 in q 2 /qmax
S-wave term and
r’s essentially
decouple
FOCUS Form Factors
*0 

D K  
Cuts 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
Very Clean Data
Systematic Checks
S-wave – varied cuts
35 fits – Sample Variance
Form Factor (3 sources)
A  0.330  0.022  0.015
1) Varied Cuts
2) Split sample
  0.68  0.07  0.05
PD , D D, mK
3) Vary MC input
Charm Backgrounds
Right sign – Wrong sign
Charm
Background
2
2
( 0.9 GeV / c )
A3 (0)
2
A1 (0)
 ( stat )  ( sys )
rV  1.504  0.057  0.039
r 2  0.875  0.049  0.064
Phys.Lett.B544:89-96, 2002
hep-ex/0207049
0.6
0.4
0.2
0
Experiment
Models
ECL
Lattice Gauge!
BBD
UKQCD
LANL
15
SPQR
Stech
KS
BKS
WSB
1
LMMS
1.2
10
APE
0.8
5
AW/GS
1.4
0
ISGW
1.6
APE
LMMS
LANL
SPQR
KS
E691
BEAT
E791
E687
E653
Rv
UKQCD
BBD
ECL
BKS
AW/GS
Stech
ISGW2
ISGW
WSB
2
ISGW2
0
E687
0.5
E691 E653
S-Wave
effects
apparent only
with high
statistics
E791
1.5
BEAT
1
Focus
2.5
R2
3
Focus
*0 

Form Factors Comparison D  K  
20
A more detailed look at the K line shape
Take advantage of the very clean signal
Previous best K* parameters
Lass (1988) K scattering
Spectra is
complicated
Mass range limit in fit
More Blatt-Weisskopf
radius info away from pole
FOCUS sees S-wave effects primarily Below K*
FOCUS PRELIMINARY
Using LASS parameters
for ER model of 
-Careful studies of resolution effects too
K* Mass
K* Width
BL-WK radius
#K* events
Scalar Fraction
Constant 
Mass and Width
Don’t change
0.00015
FOCUS PRELIMINARY M K *  0.89463  0.000300.00016 GeV / c
Systematics by varying cuts,
background contribution, shapes
00051
K *  0.04751  0.0008100..00022
GeV / c 2
2
FOCUS Form Factors
DS   
- Event by Event version of discrete transform method
- No evidence for S - wave
- Backgrounds higher (cut on M())
rV  1.549  0.250  0.0148
r 2  0.713  0.202  0.284
 ( stat )  ( sys )
Phys.Lett.B586:183-190, 2004
hep-ex/0401001
Ds   form factor enigma
ISGW2
LMMS
CLEO
7
8
LMMS
0.5
9
ISGW2
3
6
E687
2
5
BKS
LMMS
1.0
BKS
1
4
E653
ISGW2
2.0
3
CLEO
2
2.5
1.5
0
1
R2
E791
0
1.5
0.5
E791
0.0
3.0
E687
E653
CLEO
2
circa 1999
R2
E791
2.5
0.5
Focus
0
3
E687
CLEO
0.5
1.0
BKS
1.5
E687
1.5
LMMS
2.0
E653
2.5
2
1
RV
3.0
Focus
ISGW2
2.5
BKS
E653
E791
3
RV
Ds   versus D+ K*l
0.0
0
1
4
5
6
7
8
9
Theoretically the Dsl form factor should be within 10% of D+ K*l . The
rV values were consistent but r2 for Dsl was  2 higher than D+ K*l .
But the (2004) FOCUS measurement has consistent r2 values as well!
Backgrounds Make a difference!
Biggest Players:
Signal, ~400 events
(red and dots)
Combinatoric Background,
~750 events (pink hatch)
Muon Misid, ~300 events
(faint black histogram)
   0  
D
A peek at:
Search for Cabibbo Suppressed Ds semileptonic decay
A Cabibbo favored
SL decay
Ds
c
s
Vcs

W


s
K
s
u u
K
K+ K- mass in KK events


Cabibbo suppressed
SL Decay

Ds
c Vcd
s
Would be a
discovery!
Right Sign
Wrong Sign
s


W
d
Note kaon
and muon
have same
sign


u u
K
K*
K  mass in K  events
What’s this?
DsK* decay is a
small WS background
component in our
previous D+K* work
Easy to see
and study
MK (GeV/c2)
Preliminary results of the search
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
data
MC
MK (GeV/c2)
With tight cuts,
After lots of the MC matched
the data away
cuts
from the K* peak.
We saw a 3.9s
excess in K* yield
in data over MC
In the loosely cut
sample, the MC
was a poor match
to the observed
WS K spectrum.
Large non-charm
contribution?
MK (GeV/c2)
(
)
If this K* excess were
 Ds  K *
 (12.9  3.3  ??? ) %
interpreted as DsK* ,

 Ds  
we would obtain...
(
)
This BR is very consistent with (10 ±1.3)%
predicted by R.J. Oakes et al. (1997) (hep-ph/9708277)
FOCUS BR Measurements
S
*0 

D K  
D  K   
events / 5 MeV/c2
events / 10 MeV/c2
*0
( D   K   ) ( DS   )
,




( D  K   ) ( D     )
Phys.Lett.B540:25-32, 2002
hep-ex/0206013
*0
( D   K   )





( D  K   )
0.602  0.010( stat )  0.021( sys )
M ( K     { })  M ( K    { })  0.18 GeV / c 2

(cuts D*  D 0  )!
DS   
DS   
Includes S-wave interference
Systematic errors :
expressed as a fraction of s st at
for D  ( DS ) :
Vary Cuts  0.71, (1.06)
Splitting Samples  1.57, (1.12)
Vary fit (Bk, ff)  1.57, (0.94)
Total (quadratur e)  2.2, (1.5)
( DS    )



( DS   )
0.54  0.033 ( stat )  0.048 ( sys )
BR Comparisons to Exp. & Models
focus
cleo
0.4
cleo2
0.6
e687
argus
/ 
0.8
BR relative to  are consistent
0.540  0.040
0.2
BR relative to K …not so good
0.9
Cleo 2
0.8
(K*l )/(K)
Cleo 2
Omega
0.7
0.620.02
0.6
Focus
Cleo 1
0.5
E691
E687
0.4
muons
0.3
E653
electrons
Argus
What about
D   K *0  

0 
D K 
?
-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)
But CLEO2 Reported

*0 

0 
D K  

0 
Using the B( D  K   )
1
From the PDG
But using PDG values we also find:
Isospin
Violation?
D K  

K 0e ( D )  K e ( D )  (25  9.7) / ns
0
FOCUS
D   K *0  


D K  
0
Reconstruct both
K S0 (   ) & K *0 ( K   )
In the FOCUS silicon
Drawback: Only about 10% of Ks>+Decays occur in the FOCUS silicon
Find Background Dominated by D>KsX

*0

0

D K  
FOCUS

D K  
is world’s best
hep-ex/0406060
Submitted to PLB
Measure:
D   K
 0.625  0.045  0.034

0 
D K  
Correct for S-Wave:
D   K *0  


D K  
0
 0.594  0.043  0.030
Use Focus K* and PDG K, compare to D0:
K   ( D  )  K   ( D 0 )  (11  11) / ns Isospin OK again
Long standing “difference” for D0 is in “wrong” direction
0


D   K 0 e 


D K  
0

 0.72  0.11
D 0  K  e 
?=1.03=?


D K  
0
 1.12  0.07
Comparison to other Experiments and Theory
Other Exp’s
Models
Focus measurements
suggest little “missing”
Semileptonic rate
PDG
D   e  (anything )  17.2  1.9%
Sum of PDG CA e modes
D   ((3 / 2) K    K 0 )e 
 12.9 11..46 %
Focus ’s as e’s
D   ((1.05) K  (1.03) K 0 )  
 14.9  1.2 %
Hard to believe PDG for
PS electron is correct
Preview of other FOCUS analysis
-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%)
D0  ( K S0  ) 
D 0     
D 0  K   
Conclusions:
• 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*)…
• Resolved some outstanding enigmas
( ff’s, V/PS Ratio, PDG rates)
• Raised some new ones (low q2 in K*,
proper S-wave description
• Looking at new things