Measurement of Br of D s → π 0 l ν, D s → K s l ν, D s → ρ l ν

Measurement of Br of Ds → π0 l ν, Ds →Ks l ν, Ds →ρ l ν

decays in Signal Monte Carlo and Generic Monte Carlo

Sudeshna GangulyAnze Zupanc

Giovanni Bonvicini

Based on my presentation to Belle General meeting, February 2014

04/30/2014

Idea• In standard model ( leptonic decay of Ds ):

1. A c quark decays into a s quark via a virtual w boson which annihilates into a Ɩ and a ν, 2. In semi-leptonic decay of Ds ,

3. Ds can make hadrons without any s-quark by: 1) Fock’s development : Ds > = c0 | c ̅s > + c1 | c ̅s q ̅q > +

c2 | c ̅s q ̅q q ̅q > +………….. 2) hadron mixing 3) higher order QCD processes

4. This analysis probes all that by looking for the decay Ds →π0 /(ρ) l ν5. For Ds → Ks

l ν

Ds → Ks l ν is a

Cabbibo suppressed decay and it shares the same final state as ρ l ν

w

Obtaining inclusive Ds sample Fully reconstruction in charm: e+ e- → cc ̅ → DtagKXfragDs

*

• Dtag (See backup for details) → D0, D+, ΛC+ (18 tag modes: involving kaons,

pions, neutral pions, protons etc.) or excited D*0, D*+

• K = K+/- , Ks0

• Xfrag = nothing, π+/- , π0 , π+/- π+/- , π+/- π0 , π+/- π+/- π+/- , π+/- π+/- π0

• All possible reconstructed DtagKXfrag combinations are made so that there total charge is +(-) 1 and these candidates do not overlap with each other. Then we calculate MR(DtagKXfrag) closest to nominal Ds

* mass.

• Ds*→Ds γ; Ds signal candidates are identified as a peak in recoil mass spectrum:

= MR (DtagKXfrag γ ) =

• All DtagKXfrag γ combinations with MR > 1.83 GeV and PR >2.8 GeV are retained for further analysis 3

Best Inclusive Ds sample: Mmiss(DtagKXfrag γ)Inclusive Ds reconstruction done as described in BN1244

Ds → π0 l ν Ds → ρ l ν Ds → Ks l ν

4

Mmiss distributions for correctly reconstructed inclusive Ds (with cate1 only) with Signal MC

Reconstruction of exclusive Ds→π0 l ν / Ks l ν / ρ l ν decay and data

sample used for analysis

Selection Criteria:

• For each DtagKXfrag γ candidate, exactly 1 charged track and one additional π0 / Ks / ρ in the rest of the event.

• Ks and ρ candidates do not overlap with inclusive Ds candidates.

• 1.95 < MR (Ds ) < 1.99 GeV

Selection of π0 (nominal mass 134.9 MeV) : 117.8 < mγγ < 150.2 MeV

5

Selections used for good Ks (nominal mass 497.6 MeV)→ π+ π- :|mππ-MKS|< 20 MeV

The dominant decay mode of ρ: ρ → π+ π- and all π+ π- combinations with invariant mass within +/-250 MeV around the rho's nominal mass (770MeV)are accepted

Signal MC samples have been generated for each of the Ds decay modes : No. of events generated 4X10^7

To determine the reconstruction efficiencies and to study backgrounds six streams of generic MC samples are used(all 4 types: charged, mixed, charm, uds).

Yield determination procedure

• Each final stage candidate in the exclusive decay mode of Ds is reconstructed explicitly except for the neutrino candidate.

• The signal yield from fit to the MM2 (Dtag K Xfrag l γ π0 /Ks /ρ) = [Pmiss(DtagKXfrag l π0/Ks/ρ)]^2 distribution between -0.3 and +0.3 GeV.

• The missing 4-momenta is given as Pmiss(DtagKXfrag l π0/Ks/ρ) = pe+ +pe−-pDtag-pK-pXfrag-pγ-pl-pπ0/Ks/ρ

• First the Eecl variable ( energy of the ECL cluster) with a selection of Eecl<0.4 eliminated about 50% of the background.

• Next the neutrino energy variable and a selection criteria of Eecl<0.4 & Enu>0.2 – the rectangular cut.

• Calculate a figure of merit(FOM), defined by S/√(S+44.56B); S and B are the signal and background candidates ( for |MM2| < 0.05 ) respectively around the zero peaking region of MM2 distribution

6

Fully reconstruction in charm: e+ e- → cc ̅ → DtagKXfrag γ (π0 /Ks /ρ) l ν

Eecl

• Eecl is the asymmetric energy between the signal photon candidate and any other photon candidate defined as:

• This extra energy is not associated to the Dtag K Xfrag γ l π0 (Ks / ρ ) system in our analysis.

• Eecl cluster with energy >50 MeV in barrel, >100 MeV in forward and >150 MeV in

backward end cap are used to calculate Eecl.

7

•With Eecl<=0.4 selection ; εS/√ εB only gives a marginal improvement for π0 l ν mode (a low background mode)

•Looked at the sources of background (dsdm variables) for each of the decay modes, •Ds →Ks e ν in Generic Monte Carlo: SIGNAL MODE: NUMBER 7 :anti-K0 e+ ν e and Ds →Ks μ ν in Generic Monte Carlo: SIGNAL MODE: NUMBER 14 :anti-K0 μ+ ν μ

Black line with Eecl<= 0.4 cut and Red line without Eecl cut in Generic Monte Carlo 8

Ds →Ks μ ν : The peaking background is coming from mode 18:anti-K0 K+

MM2 Plots with Generic Monte Carlo(6 streams of MC) for a Dtag K Xfrag γ μ Ks system (BACKGROUND MODES)

Eecl<= 0.4

Ds →ρ μ ν: the dominant background mode: K+ K- μ+ ν μ (16); Other dominant background is f0 l ν; which is not in generic MC

Ds → π0

μ ν

• Conclusions with Eecl<=0.4 selection:

9

Ds →Ks μ ν channel has a problem of peaking background at |MM2| = 0. [Ds →Ks e ν mode: εS/√ εB = 0.77 Ds →Ks μ ν mode: εS/√ εB = 0.76 : no improvement]

Ds →ρ l ν channel has high background with a shoulder near |MM2| = 0. [Ds →ρ e ν mode: εS/√ εB = 0.90 Ds →ρ μ ν mode: εS/√ εB = 0.95 : no improvement] • Ds → π0 l ν decay channel is a low background channel.[Ds →π0 e ν mode : εS/√ εB = 1.09 ( a 9% improvement) Ds →π0 μ ν mode : εS/√ εB = 1.24 ( a 24% improvement)]

•So we try a new cut with neutrino energy.

Neutrino energy

• The neutrino energy for a Dtag K Xfrag γ l Ks (ρ ) system in the rest frame is defined as : •E 𝞶 l = (MDs

2 - MKs(ρ)l2)/ 2 MDs

10

The low E 𝞶 background events correspond to |MM2| == 0 region, we can obtain a significant background loss by choosing events with lower E 𝞶Conclusions with “Eecl<=0.4 & Enu>=0.2” selection:

• The problem of a peaking background at |MM2| = 0 in Ds →Ks μ ν decay can be removed applying this selection criteria.

• For Ds →ρ l ν channel, the high background with a shoulder near |MM2| = 0 is reduced.

2-dimensional scatter plots(y axis: MM2; x axis: Eecl_ks)

11

Ds → Ks e ν Signal MC Ds → Ks e ν Backgrounds (6 streams of generic MC)

Ds→ Ks μ ν Signal MCDs → Ks μ ν Backgrounds (6 streams of generic MC)

2-dimensional scatter plots(y axis: MM2; x axis: Enu_lepton_ks)

12

Ds → Ks e ν Signal MC Ds → Ks e ν Backgrounds (6 streams of generic MC)

Ds → Ks μ ν Signal MC Ds → Ks μ ν Backgrounds (6 streams of generic MC)

2-dimensional scatter plots(y axis Enu_lepton_ks; x axis: Eecl_ks)

13

Ds → Ks e νSignal MC

Ds → Ks e ν Backgrounds (6 streams of generic MC)

Ds → Ks μ νSignal MC

Ds → Ks μ ν Backgrounds (6 streams of generic MC)

14

Selection criterion

No. of signal events

No. of background events

ε_signal ε_background FOM(S/√S+44.6B)

1 Eecl < 6.9 *Enu -1.5

3422 (out 3778)

29(out of 169)

0.906 0.172 49.8

Ks μ ν

Ks e ν

Ks e ν : Very low background; No Cut

Selection criterion




1 Eecl < 6.5 *Enu +1.7

4355(out of 4361)

13( out of 14)

0.998 0.928 61.9

MM2 for a Dtag K Xfrag γ e Ks system fitted with a Crystal ball and two Gaussian

functions(Signal MC:4X10^7)Ds →Ks e ν Ds →Ks μ ν

15

χ2 = 0.663χ2 = 1.416

with Eecl < 6.9*Enu – 1.5 with no cut

MM2 for a Dtag K Xfrag γ μ Ks system fitted with a Crystal ball and two Gaussian functions(Signal MC:4X10^7)

MM2 fitted with the signal function combined with a background linear polynomial function (Generic MC-6 streams: signal mode : number 7 : anti-K0 e+ ν e )

MM2 fitted with the signal function combined with a background linear polynomial function (Generic MC-6 streams: signal: number14 anti-K0 μ+ ν μ )

χ2 = 0.668 χ2 = 0.329

MM2 for a Dtag K Xfrag γ l Ks system fitted with a Crystal ball added to a linear polynomial function for the muon mode and with a Gaussian added to a

linear function for the electron mode (Generic MC-6 streams: background modes)

Ds →Ks e ν Ds →Ks μ ν

16

χ2 = 0.389χ2 = 0.359

with no cut with Eecl < 6.9*Enu – 1.5

Cross-checking of the Branching ratio of D s → Ks

l+ 𝞶e decay in MC(using the best selection criteria)

Branching fraction of D s → Ks e ν decays:

Expected Branching ratio of D s → Ks l+ 𝞶e

; B = 3.7 X 10-3

17

Estimated combined Belle Stat. error is 1.5X 10-4

Branching fraction of D s → Ks μ ν decays:

B ± δB (Statistical only) = (3.63±0.23)X10-3 B ± δB (Statistical only) = (3.72±0.20)X10-3

18

Selection criterion




1 Eecl < 4.8 *Enu – 0.4

4058(out 4413)

762(out of 1031)

0.919 0.739 20.8

ρ μ ν

ρ e ν

ρ e ν : low background: No Cut

Selection criterion




1 Eecl < 5.1*Enu +1.0

5308(out of 5351)

405( out of 422)

0.991 0.959 34.7

2-D scatter plots are in the backup slides

MM2 plot for Ds → ρ μ ν with 6 streams of Generic MC: only background modes

Efficiency = 74%Efficiency = 92%

19

MM 2 plot for Ds → ρ μ ν with Signal MC

MM2 for ρ l ν : Blue line with Eecl < 4.8*Enu – 0.4 cut and Red line without Enu cut, only Without this cut.

Backup slides

MM2 for a Dtag K Xfrag γ e ρ system fitted with a Crystal ball and two

Gaussian functions(Signal MC:4X10^7)

Ds →ρ e ν Ds →ρ μ ν

20with Eecl < 4.8*Enu – 0.4 with no cut

χ2 = 1.416χ2 = 2.267

MM2 fitted with a Crystal ball and a landau function (Generic MC-6 streams: background modes)

χ2 = 0.967

MM2 for a Dtag K Xfrag γ μ ρ system fitted with a Crystal ball and two Gaussian functions(Signal MC:4X10^7)

MM2 fitted with a Crystal ball and a landau function (Generic MC-6 streams: background modes)

χ2 = 0.757

21

Selection criterion




1 Eecl < -4.6 *Enu + 4.2

2185(out 2473)

52(out of 87) 0.88 0.597 32.6

π0 μ ν

π0 e ν Selection criterion No. of

signal events



1 Eecl<-4.0*Enu+4.2 2368(out of 2447)

41( out of 62)

0.967 0.66 36.6

Ds →π0 μ ν

MM2 for a Dtag K Xfrag γ μ π0 system fitted with a background linear function and a signal function(Generic MC-6 streams)

22

Fit results are shown in the next slide

With Eecl<= -4.6*Enu+4.2

Ds →π0 μ ν

MM2 for a Dtag K Xfrag γ l π0 system fitted with Crystal ball and two Gaussian functions(Signal MC: 4X10^7)

χ2 = 2.690χ2 = 0.954

• Fit result : MM2 for a Dtag K Xfrag γ μ π0 system fitted with a background linear function and a signal Gaussian function(Generic MC-6 streams)

• EDM=3.65521e-05 STRATEGY= 1 ERROR MATRIX ACCURATE• EXT PARAMETER PARABOLIC MINOS ERRORS• NO. NAME VALUE ERROR NEGATIVE POSITIVE• 1 a0 1.21310e-02 9.10972e-01 at limit 2.76888e-01• 2 a1 -1.31653e+00 1.88251e+00 -1.75494e+00 2.04943e+00• 3 fO -3.71207e-02 2.47444e-02 -2.39079e-02 2.55819e-02• 4 yld 3.73024e+02 1.93141e+01 -1.90057e+01 1.96242e+01• ERR DEF= 0.5• MINOS: status = 0

23

So N_s( Signal Yield) = -13.8+(-) 9.23


Ds →π0 e ν

MM2 for a Dtag K Xfrag γ e π0 system fitted with a background linear function and a signal function(Generic MC-6 streams)

24



Ds →π0 e ν

MM2 for a Dtag K Xfrag γ e π0 system fitted with Crystal ball and two Gaussian functions(Signal MC: 4X10^7)

χ2 = 0.925 χ2 = 1.288

• Fit result : MM2 for a Dtag K Xfrag γ e π0 system fitted with a background linear function and a signal Gaussian function(Generic MC-6 streams)

• NO. NAME VALUE ERROR STEP SIZE VALUE• 1 a1 2.38530e+00 4.58179e-01 3.36359e-05 2.40852e-01• 2 a2 1.45757e+00 2.68091e+00 8.93050e-04 1.46278e-01• 3 fO -2.61217e-02 3.60411e-02 3.04862e-04 -6.17071e-01• 4 yld 2.93997e+02 1.71463e+01 5.43898e-07 -1.56737e+00• ERR DEF= 0.5

25

So N_s( Signal Yield) = -7.67+(-) 10.59


Upper limit on the Branching ratio (at 90% CL) for the D s → π0 μ+ 𝞶e

decay (statistical only)

Inclusive Ds sample :N( inclusive)= number of inclusively reconstructed Ds mesons in the first step = 95000 known tags from BN1244

N( inclusive)= number of inclusively reconstructed Ds mesons in the first step = 601665 in 6 streams of Generic MC

Efficiency ε from signal MC (4X10^7 events) = 3200/28989= 0.110

N(exclusive) = number of exclusively reconstructed D s → π0 μ ν decays = (-13.8+-9.23) events in 6 streams of Generic MCThe upper limit on the branching ratio B(D s → π0 μ 𝞶e ) < 5.6X 10-4 (90% CL)

26


Inclusive Ds sample :N( inclusive)= number of inclusively reconstructed Ds mesons in the first step = 95000 known tags from BN1244

N( inclusive)= number of inclusively reconstructed Ds mesons in the first step = 601665 in 6 streams of Generic MC


N(exclusive) = number of exclusively reconstructed D s → π0 μ ν decays = (-7.67+-10.59) events in 6 streams of Generic MCThe upper limit on the branching ratio B(D s → π0 μ 𝞶e ) < 5.6X 10-4 (90% CL)

Upper limit on the Branching ratio (at 90% CL) for the D s → π0 e+ 𝞶e


With Eecl<=-4.0*Enu+4.2

Estimated combined Belle limit is 3.9X 10-4 (90% CL)

• Work done so far: • Established and optimized selection method for each channel • Estimated expected error for Ks l ν (factor of 7 better than world average)• Estimated expected upper limit on the Branching ratio (at 90% CL) for π0 l ν is

2.27X 10-4 (about a factor 4 better than Cleo-c)• Started BN1344• “Opened the box”, the final data sample collected near ϒ(4S) and ϒ(5S)

resonances with Belle detector at the KEKB asymmetric energy e+e- collider, with total luminosity of the sample being 913 fb^-1 .

• Future plans: 1. ρ l ν limit not estimated, it will depend on fitting the f0 component plus

interference terms (not included in Generic MC). 2. Present the absolute branching fraction measurements for each of the decay

modes.

27

Reference : “Measurements of branching fractions of leptonic and hadronic Ds+ meson decays and extraction of the Ds+ meson decay constant” by Belle Collaboration arXiv:1307.6240v2[hep-ex] 1 Oct 2013

28

http://inspirehep.net/search?p=collaboration:'Belle'&ln=en

Backup slides

29

• The selection criteria π+/- , K+/- , π0 , Ks0 , Λ, p, γ used to reconstruct Dtag are

summarized in section 4.1, BN1244v3.

Tagging method Dtag (BN1244) : The tagging charmed hadron can be D0, D+, ΛC

+ , or excited D*0, D*+.

The ground state Dtag hadrons, D0, D+, ΛC+ are reconstructed in total 18 hadronic decay modes.

Large backgrounds avoided by using modes with up to one π0, only.

D*0, D*+ decays are identified by reconstructing D*+ → D0 π + , D+π0 and D*0 → D0 π0 , D0ϒ. Accept Dtag candidate with invariant mass between 1.82 GeV and 1.91 GeV(1.80 and 1.93 GeV if one of decay products is π0 ) and p* > 2.3(or 2.5)GeV.

30

Backup slides

Primary kaon reconstruction

• After the reconstruction of the Dtag hadrons, a strangeness balancing kaon is required.

• The strangeness balancing kaon can be K+/- , Ks

0 candidates which do not overlap with the Dtag candidate.

• The selection criteria for the strangeness balancing kaon :

• K+/- : p>0.1 GeV• L K/ π = atc_pid(3,1,5,3,2) >

0.6• L e = eid < 0.9 (electron veto)• L K/ p = atc_pid(3,1,5,3,4) >

0.1 (proton veto)

• Ks0 : loose goodKs selection

• |mππ-MKS|< 20 MeV• Vertex fit is performed

31

The tracks and π0candidates left in the event, not overlapping with the Dtag K system can be used to reconstruct the Xfrag candidates in the following modes: • nothing • π+/- • π0 • π+/- π0 The modes which contain only one π0 and only up to 3 charged pions are allowed to form Xfrag system to discard a large combinatory background. The selection criteria for all charged pions and neutral pion making up the Xfrag system is the same as given in BN1244[XXX].

Xfrag reconstruction

Fully reconstruction in charm: e+ e- → cc ̅ → DtagKXfragDs*

Backup slides

Selection Criteria For Inclusively Reconstructed Ds candidates:

e+ e- cc ̅ DtagKXfragDs*, Ds

* Ds γ e+ e- cc ̅ events containing Ds mesons proceed via :

A photon candidate consistent with the decay of Ds*→Ds γ which does not overlap with the

DtagKXfrag system, must satisfy :

1. E γ > 120 MeV2. E9/E25 > 0.753. The cosine of the angle between the direction of tagged charm hadron and the direction of the photon candidate is negative, as the signal photon should be in the signal hemisphere of the event.4. All DtagKXfrag combinations with Pmiss(DtagKXfrag γ ) > 2.8 GeV Mmiss(DtagKXfrag γ ) > 1.83 GeV can be used.

32

Backup slides

Eecl plotsDs→ π0 e ν

6 streams of Generic MC Efficiency ε = 46%

Signal MC Efficiency ε = 74%

33

Ds→ π0 μ ν Efficiency ε = 77% 91.3%

Ds→ π0 e ν

Ds→ π0 μ ν Efficiency ε = 47%

Cut at Eecl = 0.4

Cut at Eecl =0.4Cut at Eecl = 0.4

Cut at Eecl = 0.4

Backup slides

Signal MC 6 streams of Generic MC

34

Ds→ Ks e ν Efficiency ε= 67%

Cut at Eecl = 0.4

Ds→ Ks μ ν Efficiency ε= 70% Efficiency ε= = 22%

Backup slidesEecl plots

Cut at Eecl = 0.4

Cut at Eecl = 0.4

Cut at Eecl = 0.4

Cut at Eecl = 0.4

Ds→ Ks e ν Efficiency ε= 22%

Ds→ Ks μ ν Efficiency ε= 18%

Ds →ρ e νEfficiency ε=67%

6 streams of Generic MC

Backup slides Eecl plots

Ds →ρ μ νEfficiency ε= 71%

Cut at Eecl = 0.4

Cut at Eecl = 0.4

Cut at Eecl = 0.4

Ds →ρ e νEfficiency ε=50%

Cut at Eecl = 0.4

Ds →ρ μ νEfficiency ε= 49%

Signal MC

35

Fractional Background Contribution in π0 l ν With Generic Monte Carlo (dsdm variable)

36

π0 e ν π0 μ ν

𝛕 + 𝞶 𝛕 (2)

𝟇 e+ ν e (4)

𝛈 e+ ν e (5)

anti-K0 e+ ν e (7)

K0 anti-K0 e+ ν e (10)

μ + 𝞶μ (1) 𝛕 + 𝞶 𝛕 (2)

𝟇 μ+ ν μ (11)

𝛈 μ+ ν μ (5)

anti-K0 μ+ ν μ (14)


Backup slides

with Eecl<= 0.4

37

MM2 Plots for a Dtag K Xfrag γ e π0 system

Ds → π0 e ν (Signal Monte Carlo) Ds → π0

e ν (6 streams of Generic Monte Carlo)

MM2 for Ks l ν : Blue line with Eecl<= 0.4 cut and Red line without Eecl cut in signal Monte Carlo

with Eecl<= 0.4

Backup slides

MM2 Plots for a Dtag K Xfrag γ μ π0 system

38

Ds → π0 μ ν (6 streams of Generic Monte Carlo)Ds → π0

μ ν (Signal Monte Carlo)

MM 2 for π0 l ν : Blue line with Eecl<= 0.4 cut and Red line without Eecl cut in Generic Monte Carlo

with Eecl<= 0.4

Backup slides

MM2 for a Dtag K Xfrag γ l π0 system fitted with Crystal ball and two Gaussian functions(Signal MC: 4X10^7)

Ds →π0 e ν Ds →π0 μ ν

χ2 = 1.496χ2 = 1.385

39

With Eecl<=0.4

Backup slides

MM2 for a Dtag K Xfrag γ e π0 system fitted with a background linear function and a signal Gaussian function(Generic MC-6 streams)

Ds →π0 e ν Ds →π0 μ ν

MM2 for a Dtag K Xfrag γ μ π0 system fitted with a background linear function and a signal Gaussian function(Generic MC-6 streams)

40


With Eecl<=0.4

Backup slides

41

Fit result 1: MM2 for a Dtag K Xfrag γ e π0 system fitted with a background linear function and a signal Gaussian function(Generic MC-6 streams)

EXT PARAMETER INTERNAL INTERNAL NO. NAME VALUE ERROR STEP SIZE VALUE 1 a0 2.02130e-01 5.81907e-01 2.15528e-02 -6.38187e-01 2 a1 1.42101e+00 3.79198e+00 5.88228e-03 1.42584e-01 3 fO -2.60707e-02 2.46990e-02 6.90975e-04 -6.16975e-01 4 yld 1.27976e+02 1.13121e+01 1.63403e-06 -1.56853e+00 5 ERR DEF= 0.5So N_s ( Signal Yield) = -3.3+(-) 3.2

Fit result 2: MM2 for a Dtag K Xfrag γ μ π0 system fitted with a background linear function and a signal Gaussian function(Generic MC-6 streams)

EXT PARAMETER INTERNAL INTERNAL NO. NAME VALUE ERROR STEP SIZE VALUE 1 a0 1.00000e+00 1.54326e-01 2 .02909e-03 1.57093e+00 WARNING - - ABOVE PARAMETER IS AT LIMIT.2 a1 7.51464e-01 4.69634e+00 1.13668e-03 7.52173e-02 3 fO 2.33465e-02 4.54002e-02 1.87376e-04 -5.26539e-01 4yld 8.29988e+01 9.11033e+00 3.74073e-07 -1.56897e+00 ERR DEF= 0.5So N_s( Signal Yield) = 1.9+(-) 3.8

Backup slides

with Eecl<= 0.4

Upper limit on the Branching ratio (at 90% CL) for the D s → π0

e+ 𝞶e


Upper limit on the Branching ratio (at 90% CL) for the D s → π0 μ+ 𝞶e


Inclusive Ds sample :N( inclusive)= number of inclusively reconstructed Ds mesons in the first step = 355163 in 6 streams of Generic MC


N(exclusive) = number of exclusively reconstructed D s → π0 μ ν decays = (-3.3+-3.2) events in 6 streams of Generic MCThe upper limit on the branching ratio B(D s → π0 e+ 𝞶e ) < 4.9X 10-4 (90% CL)

Inclusive Ds sample :N( inclusive)= number of inclusively reconstructed Ds mesons in the first step = 355163 in 6 streams of Generic MC

Efficiency ε from signal MC (4X10^7 events) = 3001/34129 = 0.088

N(exclusive) = number of exclusively reconstructed D s → π0 e + ν decays = (1.9+-3.8) in 6 streams of Generic MC

The upper limit on the branching ratio B(D s → π0 μ 𝞶e ) < 3.6X 10-4 (90% CL)

Estimated combined Belle limit is 3X 10-4 (90% CL)

42

With Eecl<=0.4

Fractional Background Contribution in Ks l ν With Generic Monte Carlo (dsdm variable)

43

Kseν Ksμν

𝟇 e+ ν e (4)


K* anti-K0 (23)

anti-K0 K+ (18)

𝟇 π+ (20)


𝟇 μ+ ν μ (11)

Backup slides

with Eecl<= 0.4

44

MM2 Plots for a Dtag K Xfrag γ e Ks system

Ds →Ks e ν (Signal Monte Carlo)

MM2 for Ks e ν : Black line with Eecl<= 0.4 cut and Red line without Eecl cut in Signal Monte Carlo

Ds →Ks e ν with Generic Monte Carlo: 6 streams of MC(SIGNAL MODE: NUMBER 7 :anti-K0 e+ ν e

Eecl<= 0.4

Backup slides

45

MM2 Plots for a Dtag K Xfrag γ μ Ks system

Ds →Ks μ ν (Signal Monte Carlo)

MM2 for Ks μ ν : Black line with Eecl<= 0.4 cut and Red line without Eecl cut in Signal Monte Carlo

Ds →Ks μ ν with Generic Monte Carlo: 6 streams of MC(SIGNAL MODE: NUMBER 14 :anti-K0 μ+ ν e

Eecl<= 0.4

Backup slides

Ds →Ks e ν: the dominant background modes are : e𝟇 + ν e (4),K0 anti-K0 e+ ν e (10)

MM 2 for Ks l ν : Black line with Eecl<= 0.4 cut and Red line without Eecl cut in Generic Monte Carlo

46

Ds →Ks μν : the dominant background modes are : 𝟇 μ+ νμ (11), K0 anti-K0 e+ ν e (17), anti-K0 K+ (18) , 𝟇 π+ (20), K* + anti-K0 (23) ; The peaking background is coming from mode 18:anti-K0 K+

MM2 Plots with Generic Monte Carlo(6 streams of MC) for a Dtag K Xfrag γ l Ks system (BACKGROUND MODES)

Backup slides

with Eecl<= 0.4

Fractional Background Contribution in ρ l ν With Generic Monte Carlo (dsdm variable)

[f0 is not in the generic Monte Carlo]

47

ρ e ν ρ μ ν

𝟇 e+ ν e (4)

𝛈’ e+ ν e (6)

K+ K- e+ ν e (9)

𝟇 μ+ ν μ (11)𝛈’ e+ ν e (13)

K+ K- μ+ ν μ (16)

Backup slides

with Eecl<= 0.4

48

MM2 Plots for a Dtag K Xfrag γ e ρ system

Eecl<= 0.4 cut Ds →ρ e ν (Signal MC) Ds →ρ e ν (6 streams of generic MC)

MM2 for ρ l ν : Blue line with Eecl<= 0.4 cut and Red line without Eecl cut in Signal Monte Carlo

Backup slides

MM2 Plots for a Dtag K Xfrag γ μ ρ system

49

Ds → ρ μ ν (Signal Monte Carlo)Ds → ρ μ ν (6 streams of Generic Monte Carlo)

MM 2 for π0 l ν : Blue line with Eecl<= 0.4 cut and Red line without Eecl cut in Generic Monte Carlo

with Eecl<= 0.4

•The fitted plots are in the back up slides. A dominant source of background in Ds → ρ l ν decay comes from Ds → f0 l ν .

Backup slides

Eecl plots for a Dtag K Xfrag γ l f0 system ( same mass cut as ρ selection; f0 is in data but not in Generic Monte Carlo)

Ds → f0 e ν Ds → f0 μ ν

Signal MC

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Backup slides

MM2 for a Dtag K Xfrag γ l f0 system ( same mass cut as ρ selection; f0 is in data but not in Generic Monte Carlo)

Signal MC

Ds → f0 e ν Ds → f0 μ ν

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Backup slides

MM2 for a Dtag K Xfrag γ l Ks system fitted with Crystal ball and two Gaussian functions(Signal MC:4X10^7)


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With Eecl<=0.4

χ2 = 0.566χ2 = 0.897

Backup slides

MM2 for a Dtag K Xfrag γ l Ks system fitted with Crystal ball and two Gaussian functions(Generic MC-6 streams: signal mode : number 7 : anti-K0 e+ ν e and

number14 anti-K0 μ+ ν μ )

Ds → Ks e ν Ds →Ks μ ν

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With Eecl<=0.4

These are not the final plots, later we have tried the neutrino energy cut on MM2 for Ds →Ks l ν with 1 streams of Generic MC

χ2 = 0.325 χ2 = 0.873

Backup slides

MM2 for a Dtag K Xfrag γ l Ks system (Generic MC-6 streams: background modes)

(With Eecl<=0.4)


Fitted with a Gaussian and a linear function

Fitted with crystal ball and a linear function

χ2 = 0.066χ2 = 0.786

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These are not the final plots, later we have tried the neutrino energy cut on MM2 for Ds →Ks l ν with 1 stream of Generic MC

Backup slides

MM2 for a Dtag K Xfrag γ l ρ system fitted with Crystal ball and two Gaussian functions(Signal MC: 4X10^7)


χ2 = 1.314 χ2 = 1.519

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With Eecl<=0.4

Backup slides

MM2 for a Dtag K Xfrag γ l ρ system fitted with Crystal ball and Landau functions(Generic MC-6 streams)


χ2 = 0.629 χ2 = 0.787

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With Eecl<=0.4

Backup slides

MM2 for a Dtag K Xfrag γ e ρ system fitted with Crystal ball function for peaking modes(6 and 9)(Generic MC-6 streams)

MM2 for a Dtag K Xfrag γ e ρ system fitted with Crystal ball function for non- peaking modes(4 and 8)(Generic MC-6 streams)

χ2 = 0.501χ2 = 0.253

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With Eecl<=0.4

Backup slides

MM2 for a Dtag K Xfrag γ μ ρ system fitted with inverted Crystal ball function for peaking modes(14,15,18,20,21)(Generic MC-6 streams)

MM2 for a Dtag K Xfrag γ μ ρ system fitted with inverted Crystal ball function for non-peaking modes(11,13,16,17,27,29)(Generic MC-6 streams)

χ2 = 0.351 χ2 = 0.384

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With Eecl<=0.4

Backup slides

Electron Neutrino energy for Ds →Ks e ν decay

Muon Neutrino energy for Ds →Ks μ ν decay

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(1 stream of Generic MC)

(Signal MC)

Backup slides

Electron Neutrino energy for Ds → ρ e ν decay

Muon Neutrino energy for Ds → ρ μ ν decay

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(1 stream of Generic MC)

(Signal MC)

Backup slides

MM2 plot for Ds →Ks e ν with eecl cut and

neutrino energy cut (Signal MC:4X10^7)

MM2 plot for Ds →Ks e ν with eecl cut and

neutrino energy cut (Generic MC- 1 stream only background modes)

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Efficiency = 96%

MM2 for Ks l ν : Black line with Enu_l_ks>=0.2 and With Eecl<=0.4 cut and Red line without enulks cut, only With Eecl<=0.4 in signal Monte Carlo

MM2 distribution with the effect of “Eecl<=0.4 Enulks>=0.2”

Efficiency = 100%

Backup slides

MM2 plot for Ds →Ks μ ν with Eecl cut and

neutrino energy cut (1 stream of Generic MC: only background modes)

MM2 plot for Ds →Ks μ ν with Eecl cut and

neutrino energy cut (Signal MC:4X10^7))

MM2 for Ks l ν : Black line with Enu_l_ks>=0.2 and With Eecl<=0.4cut and Red line without enulks cut, only with Eecl<=0.4 in 1 stream of Generic Monte Carlo

Efficiency = 46%

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Efficiency = 97%Eecl<=0.4 Enu>=0.2

MM2 plot for Ds → ρ e ν with Eecl cut and neutrino energy cut (Signal MC: 4X10^7)

MM2 for ρ l ν : Black line with Eecl<= 0.4 cut and Enu_l_rho>=0.2 and Red line without Enulrho cut, only with Eecl<= 0.4 in 1 stream of Generic Monte Carlo

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MM2 plot for Ds →ρ e ν with Eecl cut and neutrino energy cut (1 stream of Generic MC)

Backup slides

Eecl<=0.4 Enu>=0.2

MM2 plot for Ds →ρ μ ν with Eecl cut and neutrino energy cut (1 stream of Generic MC)

MM2 for ρ l ν : Black line with Eecl<= 0.4 cut and Enu_l_rho>=0.2 and Red line without enulrho cut in Generic Monte Carlo

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MM2 plot for Ds → ρ μ ν with Eecl cut and neutrino energy cut (Signal MC: 4X10^7)

Backup slides

Eecl<=0.4 Enu>=0.2

MM2 for a Dtag K Xfrag γ l ρ system fitted with signal function(Generic MC-1 streams) [all background modes]

with Eecl<= 0.4 and Enu_l rho>=0.2 selection

MM2 for D s → ρ e ν MM2 for D s → ρ μ ν

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Backup slides

Best selection criteriaAfter producing the two dimensional scatter plots between MM2 Vs. Eecl, MM2 Vs. Enu and Enu Vs. Eecl, with signal MC and 6 streams of generic MC, we searched for the best selection criteria based on the maximum value of Figure Of Merit (FOM), defined by S/√(S+44.6*B), where S and B are the number of signal and background candidates ( for |MM2|<0.05), respectively around the zero peaking region of MM2

distribution, out of 10,000 combinations of Eecl and Enu.

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Modes Best Selection criteria

Ks μ ν Eecl < 6.9 *Enu -1.5

Ks e ν No cuts

ρ μ ν Eecl < 4.8 *Enu -0.4

ρ e ν No cuts

π0 μ ν Eecl < -4.6*Enu+4.2

π0 e ν Eecl<-4.0*Enu+4.2

MM2 plot for Ds → Ks μ ν with

6 streams of Generic MC: only background modes

Efficiency = 17%

Efficiency = 91%

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MM 2 plot for Ds → Ks μ ν with

Signal MC

MM2 for Ks l ν : Blue line with Eecl < 6.9*Enu – 1.5 cut and Red line without Enu cut, only Without this cut.

Backup slides

Best cut plots

2-dimensional scatter plots(y axis: MM2; x axis Eecl)

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Ds → ρ e νSignal MC

Ds → ρ e ν Backgrounds (6 streams of generic MC)

ρ l ν

Ds → ρ μνSignal MC

Ds → ρ μ ν Backgrounds (6 streams of generic MC)

Backup slides

2-dimensional scatter plots(y axis: MM2; x axis Enu)

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Ds → ρ μνSignal MC

Ds → ρ μν Backgrounds (6 streams of generic MC)

Backup slides

2-dimensional scatter plots(y axis Enu_electron_rho; x axis: Eecl_rho)

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Ds → ρ μ νSignal MC

Ds → ρ μ ν Backgrounds (6 streams of generic MC)

Backup slides

Fractional Background Contribution in π0 l ν With Generic Monte Carlo (dsdm variable)

with best selection

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Ds →π0 μ ν Ds →π0 e ν

Cross-checking of the Branching ratio of D s → Ks e+ 𝞶e

decay in MC

Inclusive Ds sample :N( inclusive)= number of inclusively reconstructed Ds mesons in the first step = 601665 in Generic MC 6 streams

Inclusive Ds sample :N( inclusive)= number of inclusively reconstructed Ds mesons = 30816 in Signal MC

N(exclusive) = number of exclusively reconstructed D s → Ks

e ν decays = 374 in generic MC (6 streams)


e ν decays = 5147 in Signal MC

𝝴 is the efficiency of reconstructing D s → Ks e ν decays given

inclusively reconstructed D s in signal MC

B ± δB (Statistical only) = (3.72±0.20)X10-3

Expected Branching ratio of D s → Ks

e+ 𝞶e ;

B = 3.7 X 10-3

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Cross-checking of the Branching ratio of D s → Ks μ+ 𝞶e decay

in MC

Inclusive Ds sample :N( inclusive)= number of inclusively reconstructed Ds mesons in the first step = 601665 in Generic MC 6 streams

Inclusive Ds sample :N( inclusive)= number of inclusively reconstructed Ds mesons = 30816 in Signal MC


μ ν decays = 265 in generic MC (6 streams)


μ ν decays = 3744 in Signal MC

𝝴 is the efficiency of reconstructing D s → Ks e ν decays

given inclusively reconstructed D s in signal MC

Expected Branching ratio of D s → Ks

e+ 𝞶e ;

B = 3.7 X 10-3

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= 3.63X10-3


(remember there are 95000 tags in data, so the estimated combined statistical error is going to be 1.5-3.8X10^-4)

B ± δB (Statistical only) = (3.63±0.23)X10-3

Measurement of Br of D s → π 0 l ν, D s → K s l ν, D s → ρ l ν

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Transcript of Measurement of Br of D s → π 0 l ν, D s → K s l ν, D s → ρ l ν