A new method for the relative phasemeasurement applied to K+K- channel

Matisse

Francesca De MoriUniversità di Torino e INFN Torino

Baldini R., Mezzadri G., Pacetti S., Destefanis M.

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Outline

Quick introduction New method Preliminary results Summary and outlook

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Quick introduction

Matisse H.

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J/ψ Strong and Electromagnetic Decay Amplitudes

Resonant contributions

ΓJ/ψ ~ 93keV → pQCD

pQCD: all amplitudes almost real [1]

QCD -> small phases forseen

Non-resonant continuum

pQCD regime

AEM

[1] S.J. Brodsky, G.P. Lepage, S.F. Tuan, Phys. Rev. Lett. 59, 621 (1987).

Courtesy S. Pacetti

If both real, continuum and resonant amplitudes must interfere

[4] M. Suzuki et al., Phys. Rev. D60, 051501 (1999) with BR data from PDG1998(MarkIII).[5] J.L.Rosner, Phys. Rev. D60, 074029(1999) with BR data from PDG1998(MarkIII).[6] Z. Metreveli et al., Phys. Rev. D85.092007(2012) Cleo-c[7] C.Zhenxing et al, BAM00153

We have investigated J/ψ →K+K- (All the amplitudes contribute) : J/ψ → PP (0-0-)

BESIII choses a model independent approach with the energy scan of the resonance(2012 data).The intereference with non-resonant continuum is probed with measurements off resonance as proposed by [8]

They are model dependent. They use the Branching ratios.No interference is forseen.

[8] H. Czyz, and J. Kühn, Phys. Rev. D80: 034035 (2009)

Scan measurement(Zhenxing et al, BAM00153)

Many esclusive decays are being studied: 𝑝 𝑝, 𝐾𝑆𝑜𝐾𝐿

𝑜, Λ Λ, K+K-, 5 π, 𝜇+𝜇−, Σ0Σ0, 𝜔𝜋0

[9] BABAR PRD 92,072008 (2015)

Previous determinations of the phase angle :

Фp = 89.6° ± 9.9° [4]

Фp = 89 ± 10 [5]

Фp = 73° + 5.0° [6]-4.5° [6]

Фp = (-109±5 )° [9 withCLEO-c]

= -97° ± 5° ;97 ° ± 5° [9 with BES]

Фp = 92° ± 12 , -92 ° ± 11

DATA-SET

By Yadi and Marco

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Boss 6.6.4.p01

DATA-SET

DATA SET

Standard selections

• IRxyI<1 cm;|Rz|<10cm

• 2 of vertexfitting<=100 and successful vtxfitting• 2 charged tracks with Q_tot=0 • p<2 GeV/c

• Cos<=0.8 Barrel acceptance

Kaon identification selections

• 0<E/p in EMC<0.8 (against electrons)• PID (TOF & dE/dx)

Prob>0.001 && Prob(K)>Prob(p) &&Prob(K)>Prob()&&Prob(K)>Prob()

Further selections

Opening angle>=179°The cosmic ray veto: abs(Tof(K+)-Tof(K-))<3 ns

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Stable since long time

AN

ALYSIS

SELECTIO

NS

8Normalized visible energy in 0.96-1.02 rangeget rid of the dimuon main bkgCut & count approach has been chosen.

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Relative phase: the K+K- case

Common approach:

BABAYAGA (BB) as generator efficiencyRATE from DATA analysis

Observed cross section

Fitted with cross section function(energy spread and ISRInside) to extract the phase plus other 2 parameters

(custom choice)

L(E))(

)()(

E

ENE obs

obs

On the resonance we can’t use the (1+δ) factor

A Remainder:

To exploit BB for ISR generation in our hadronic channel:

EFFICIENCY DEPENDS STRONGLY ON GENERATION MINIMUM ENERGY (E_min) AND ON INPUT PARAMETERS THAT ARE THE OBJECT OF THEMEASUREMENT.But:• Recursive procedure• Small phase spacebecause of BB authors CAVEAT

The efficiency (with ISR BB) approachesthe efficiency w/o ISR simulation whilethe E_min (minimum energy for generation, i.e the complemetary ofthe available energy for ISR radiation)is becoming larger.

Cross section of the process inside

CME(MeV)

CME(MeV)

BB has not been developed for our hadronic processes. This is a useful extensionThanks to BB authors and professor Ping Wang.

BUT

BABAYAGA authors CAVEAT is : relable in a small energy range around theInput center of mass energy . Reduced phase space in generation is the solution

The problem is how to take into acccount the eventsoutside this tight selection (due to ISR)

Depero

A new method to measure the Relative Phasebetween Strong and Electromagnetic amplitudes

In J/ψ decays

We have worked to a comprehensive approach that can be used for the available channels. The first application has been done on K+K- channel

The “ADVANTAGES” of this APPROACH:♥ BabaYaga is used (if available) with ISR and Beam energy spread

few modifications depending on channelok for ppbar, K+K-, (on the way for LLbar).Otherwise a custom generator can be used (KAMI) developed for this measurement

♥ Full PHASE space no more minimum energy dependence

♥ Only once in BOSS chain (SIM+REC+ANA) no matter what your fitting results are

♥ Efficiency is taken into account in prediction: the experimental rate is fitted

These features cure most of the problemsthat came out in the usual approach

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First we tried it with K+K- and BABAYAGA generator

NEW weightedweights of each event are brought out (thanks to the precious help of Carlo Calame)

From Carlo

The angular distribution was added by HIT or MISS in BB .

Normalization of BABAYAGA weights requires:

We want to reweight the events not to change their total number!

(1)

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𝑤𝑒𝑖𝑔ℎ𝑡

𝑁𝑔𝑒𝑛= 1

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Further check with a custom generator (KAMI) for this measurement.

For ISR based on Bonneau Martin (Nucl Phys B27 (1971)381 )and Touschek (Nuovo Cim, LIB2 (1967) ) formulas. It has been checked the equivalence with KKMC (Weiping Wang (USTC) BAM-00159 ).It includes Energy Spread effect and CME error.

IT WAS DEVELOPED FOR THIS MEASUREMENT!

For each generated event are stored in an ASCII file (in coll. with Calame Carlo)

four-momenta of final particles (from which energy after ISR WISR) wheight (P)

SIM,REC,ANALYSIS in BOSS framework

By Manual Generator

Survivors (with their WISR and P)

FITTING ROUTINEPRELIM.RESULTS15

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Efficiency check

Flat efficiency!!!!What is expected

CME(MeV)

The fitting procedure

R(E) is the mean of σ(WISR) corrected by an

efficiency term

Input for each selected (by analysis algorithm) event :• energy after ISR (WISR)• weight

ISR+BEAM ENERGY SPREAD with BABAYAGA (KAMI) generator

For each WISR : c.s. calculationWeighted by P (from BB)

The cross.sec. is calculated by afunction of Relative phase φ, cross section of continuum

@3 GeV σ, branching ratio BR

For the continuum parametrization with power law of the energy

For eachnominalEnergy ,E

MINUITminimization17

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Rate=𝑁𝑠𝑖𝑔

ℒ

Table of the measured rates

Statistical errors only

Energy Rate (pb) Energy Rate (pb)

1 9.141 ± 0.857 9 328.711 ± 17.344

2 10.035 ± 0.918 10 607.255 ± 28.413

3 8.478 ± 0.785 11 267.384 ± 14.947

4 9.350 ± 1.494 12 139.966 ± 14.659

5 7.415 ± 0.762 13 42.067 ± 5.437

6 5.942 ± 0.680 14 25.278 ± 3.610

7 35.180 ± 4.274 15 16.880 ± 3.435

8 122.004± 9.370 16 14.129 ± 3.405

Preliminary results

Matisse

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φ= (91±8)°BR= (3.4±0.1)X10-4

σ(3GeV)= (25.7±1.4)pb

χ2 /NDF=1.12φ= (-91±7)°BR= (3.7±0.1)X10-4

σ(3GeV)= (25.7±-1.4)pb

χ2 /NDF=1.12

Needed to refine χ2 def introducing systematic errors

Exp

. Rat

e(p

b)

CME(MeV)

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Results with BB

CONTINUUM XS: Born XS of USTC (Dong Liu) presented @Wuhan: 23.8+-1.9+-1.0 pbcompatible within the errors32.2±2.7±1.2 pb (2.9-3.0GeV) ([*]BABAR PRD92,072008(2015))

21.7±1.6±0.6 pb (3.0-3.1GeV)

Branching Ratio:FROM CLEO-c data (2.86±0.09 ±0.19) X10-4 (ψ(2S)J/ψππ .. interference free) PRD 85,

092007 (2012) [#]

FROM BABAR [*]BR=3.50±0.20±0.12 X10-4 (with interference correction 3.36 is measured)PDG mean=2.70 ±0.17 X10-4

Peking BAM00153 :2.44±0.01±0.09 X10-4

PHASE(-97±-5)°(using BES KsKL) [*](-109±5 )°(using CLEOKsKL) [*]

From CLEO-c:( 73.5+5-4.5)° [#]PEKING BAM00153 :(92±12 )°,(-92±11)°

The effect of the weightResults’ comparison with previous ones

BR=3.4+-0.1 X10-4 (pos. phase), BR=3.7+-0.1 X10-4 (neg.phase)

σB(3GeV)= 25.7+-1.4 pb

(91+-8)°, (-91+-7)°

Indirect measurements22

A comparison with another generator (BM with Bonneau Martin approch)THIS IS ONLY A FURTHER CHECK FOR BABAYAGA THAT IS INTENDEDTO BE USED.

.

Depero

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Etim’s results with KAMIEx

p. R

ate

(pb

)

CME(MeV)

φ= (75+-14)°BR= (3.34 ± 0.09)X10-4

σ(3GeV)= (28.5±1.4)pb

χ2 /NDF=1.62φ= (-76±13)°BR= (3.74±0.10)X10-4

σ(3GeV)= (28.5±1.4)pb

χ2 /NDF=1.62

To do:

• Rewrite χ2 to take into account systematic error and center of mass energy error (for BB);

• Study parameters correlation;

Depero 25

H

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• New pieces of understanding of this complex argument have beenadded• Preliminary results have been achieved with the new method for this measurement (two generators compatible within the errors)• They are in disagreement with respect to BR with Peking analysis

(BAM00153)• Another application to ppbar channel (Destefanis Marco presentation in

Charmonium session tomorrow)• A new result using Λ Λ and KAMI custom generator is on the way(Giulio Mezzadri)

Many thanx to the Phase Working Group for their support!

matisse26