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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.
1
4
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
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
7
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.
9
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
12
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)
13
𝑤𝑒𝑖𝑔ℎ𝑡
𝑁𝑔𝑒𝑛= 1
14
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
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
19
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
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)
21
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
23
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
• i
• 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