Study of the semileptonic decaysat 4170 MeV

Koloina Randrianarivony

Marina Artuso

(Syracuse University)

2

Motivations

• Apply our techniques to other semileptonic decays.

• Study the modes that haven’t been seen yet.

3

Ks

K+K-)-

+--

K*K*(KsK-+-)-

Analysis Techniques

e+ e- (1--)

Ds+* (Ds

+) + ...Ds-(Ds

-*)

(K+K-) e+ , K*0(K+-) e+, K0(+-) e+

SIGNAL SIDE

TAGGED SIDE:

+ CC Event

The same 8 modes as in Ds+ →+ CBX 06-36

And '(+-) e+

4

Selection criteria

Data sample

~310 pb-1 at ~4170 MeV

Track Quality Cuts:

• Hit fraction > 0.5• Good fit• |d0|<0.5cm and |Z0|<5.0cm• |cosθ| < 0.93 • |p| >0.04 GeV

Particle ID

• Both dE/dX & RICH PID if |p| > 0.7GeV

• dE/dX PID if 0.2 < |p| < 0.7 GeV

• 4σ dE/DX consistency cut if |p| < 0.2 GeV, from Radia’s analysis (CBX 05-24).

PID for both Kaon and Pion. | Mass-PDG|< Г=0.050

GeV

e

electron ID.|p| > 0.2GeV.FRICH ≥ 0.8

PID for both Kaons. | Mass-PDG|< 2x Г=0.01

GeV

'

Mass constrained fit for .

Add 2 opposite charged PID Pions.

K0

Use standard VXFit Package.

5

MM*2 = (Ecm – ED - E )2 – (- pD – p)2

Look for any extra photon and select events within ± 2.5 σ

These are our number of tags

MM*2 (GeV2)

Signal MC KK - K

*e

50% -tag

50% -he

Alpha and N are fixed from fully reconstructed Ds

-Ds*+ events

where one Ds is ignored (CBX 06-36)

Cut on Mbc Є [2.015, 2.067]

Look at the invariant mass of the tags and cut on 2-2.5 depending on

the modes

6

MM*2 per modes for Ds→ K*0e

MM*2 (GeV2)

SIGNAL MCN

umbe

r of

Eve

nts

7

MM*2 (Data)

MM*2 (GeV2)

The same number of tags as Nabil: 18645 ± 426N

umbe

r of

eve

nts

8

MM2

MM2 (GeV2)

Get ± 2.5 effective sigma = f11 + (1-f1)2

# of semileptonic events, the effective sigma will be used for the rest of the modes to get the sum.

Signal MC KK - K

*e

50% -tag

50% -he

On the signal side

Fit with a 2 gaussian

Kinematic fitting is used on tag and signal sides

9

Use of sideband subtraction

MM2 (GeV2)

From sidebands

From signal side

Ds+→ K*0e+

GENERIC MC

10

DsK*0e Efficiencies

We get the weighted average SL efficiency

= (28.34 ± 0.27)%

SL Effificiency K*0 vs. Modes

0

5

10

15

20

25

30

35

0 2 4 6 8 10

M odes

Eff

icie

nc

y (

%)

Mode1

Mode 2

Mode3

Mode4

Mode5

Mode6

MOde7

Mode8

11

Using our efficiencies and

Comparison with the generic MC for DsK*0e

With NTags = 187158 ± 1052

NSignal = 35 ± 6

And SL = (28.34 ± 0.27)%, we get

Generic-MC Br (Ds+ → K*0(K)e+) = (8.6 ± 1.6)%

Input BrMC(Ds+ → K*0(K)e+) = 7 x 10-4

* The number of events are sideband subtracted

12MM2 (GeV2)

MM2 for Ds+ → K*0(K)e+ (Data)

7 signal events

0 background from the sidebands

K+- mass Є [0.846, 0.946] GeV

Num

ber

of e

vent

s

13

Comparison ISGW2 model vs. Simple Pole Model

ISGW2

SLPOL

P (GeV)

Dse Analysis

14

Dse Efficiencies

Semileptonic efficiencies

Eff SL in PhiEnu

-1

1

3

5

7

9

0 0.2 0.4 0.6 0.8 1 1.2

Phi Mom (GeV)

Eff

icie

ncy (

%)

15

Comparison with Generic MC for Dse

P NSL * Bi (Ds→e)(%)

0.0 – 0.2 4 0.66 ± 0.34

0.2 – 0.4 54 0.54 ± 0.07

0.4 – 0.6 144 0.41 ± 0.04

0.6 – 0.8 128 0.39 ± 0.04

> 0.8 44 0.47 ± 0.36

Total 374 2.49 ± 0.36

Using our efficiencies and

With NTags = 187158 ± 1052

Input Generic Br(Ds→e) = 2.02 %

* The number of events are sideband subtracted

16MM2 (GeV2)

MM2 for Ds+ → (KK)e+ (Data)

47 signal events

0 background from the sidebands

K+K- mass Є [1.010, 1.030] GeV

Num

ber

of e

vent

s

17

DsK0e Efficiencies

Efficiecencies K0s vs. Modes

05

1015202530354045

0 2 4 6 8 10

Modes

Eff

icie

nc

y (

%)

mode1

mode2

mode3

mode4

mode5

mode6

mode7

mode8

We get the weighted average SL efficiency

SL = (33.15 ± 0.24)%

18

Comparison with the generic MC for DsK0e

With NTags = 187158 ± 1052

NSignal = 52 ± 7

And SL = (33.15 ± 0.24)%, we get

Generic-MC Br (Ds+ → K0()e+) = (0.23 ± 0.03)%

Input BrMC(Ds+ → K0()e+) = 0.2%

Using our efficiencies and

* The number of events are sideband subtracted

19MM2 (GeV2)

MM2 for Ds+ → K0()e+ (Data)

10 signal events

8 background from the sidebands

+- mass Є [0.48765, 0.50765] GeV

Num

ber

of e

vent

s

20

Ds'e Efficiencies

SL eta' e nu efficiencies vs. Modes

0

5

10

15

20

25

30

0 2 4 6 8 10

Modes

Eff

icie

nc

y (

%) mode1

mode2

mode3

mode4

mode5

mode6

mode7

mode8

We get the weighted average SL efficiency

SL = (21.64 ± 0.26)%

21

Comparison with the generic MC for Ds'e

With NTags = 187158 ± 1052

NSignal = 56 ± 7

And SL = (33.15 ± 0.24)%, we get

Generic-MC Br (Ds+ → '()e+) = (0.8 ± 0.1) %

Input BrMC(Ds+ → '()e+) = 0.9%

Using our efficiencies and

* The number of events are sideband subtracted

22MM2 (GeV2)

MM2 for Ds+ → '()e+ (Data)

5 signal events

0 background from the sidebands

K+- mass Є [0.950, 0.964] GeV

Num

ber

of e

vent

s

23

Branching Fractions from Data (1)

P NSL * Bi (Ds→e)(%)

0.0 – 0.2 0 0

0.2 – 0.4 4 0.40 ± 0.20

0.4 – 0.6 16 0.46 ± 0.12

0.6 – 0.8 25 0.77 ± 0.16

> 0.8 2 0.22 ± 0.15

Total 47 1.86 ± 0.32

With a number of tags = 18645 ± 425

Due to a very small efficiency at p< 0.2 GeV, we modeled the partial branching fraction by taking the fraction of yield in that range to yield in

the rest of the momentum intervals. We estimate it as:

Br(p <0.2 GeV) (Ds→e) = (0.8 ± 0.8 (syst))%

Br(Ds→e) = (2.6 ± 0.3)%

Compare to PDG 06 Br(Ds→e) = (2.4 ± 0.4)%

24

Branching Fractions from Data (2)

SL Decays NSL* Br (%) Br P.D.G 06 (%)

Ds+ → K*0(K)e+ 7 0.19 ± 0.07 ─

Ds+ → K0()e+ 10 0.47 ± 0.15 ─

Ds+ → '()e+ 5 0.71 ± 0.32 1.08 ± 0.35

With a number of tags = 18645 ± 425 and

25

Summary and Predictions

• Br(Ds→e) = (2.6 ± 0.3)%• Br(Ds

+ → K*0(K)e+) = (0.19 ± 0.07)%• Br(Ds

+ → K0()e+) = (0.47±0.15)%• Br(Ds

+ → '()e+) = (0.71±0.32)%And with Br(Ds

+ → e+) = 3.3%

We have Br(Ds+→Xe+)excl = (7.27 ± 0.84)%

With a mean life τ = 0.5 ps, we get

Г = 0.1294 ± 0.0169 ps-1

Г+ = 0.1551 ps-1 x 0.5ps = 0.077 7.7%