Document 7659591
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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(cosV):
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
MISIDMCS 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 m2 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 cosV , 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 0.000300.00016 GeV / c
Systematics by varying cuts,
background contribution, shapes
00051
K * 0.04751 0.0008100..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 Dsl form factor should be within 10% of D+ K*l . The
rV values were consistent but r2 for Dsl 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?
DsK* 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 DsK* ,
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
0.620.02
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