Status of K±±

E. De Lucia

BR(K±±) = (21,13 ± 0.14)% BR/BR = 6,6x10-3

• Self-tag on one side using K- (nuclear interactions)• Vertex with 2 tracks in DC on the signal side

Strategy

Fitting the distribution of the momentum of the secondary track (p*) in the kaon reference frame we can extract BR(K±±)

The selection efficiency is only related to DC reconstruction:• tracking efficiency • vertex efficiency

Method:

2) Use the two “-clusters” sample

a) hp: and have the same resolution function b) p*( mass) distribution for peakc) p*( mass) distribution for peak

peak vs p*( mass)

p* (MeV/c)

MC

peak fit with p*( mass)

MC

p* (MeV/c)

In order to extract the number of decays?

1) Check the estimate of the background - require a in the calo and measure the efficiency2) Take into account the 3-body decays contribution - fit the distribution down to 190 MeV in order to have 3-body decays contribution only from kl3 channel

The fit uses the MC shape for the 3-body decays contribution

MC study of the fit

190 pb-1

p*(MC-FIT comparison

p* (K self-tag) p* (K self-tag)

Events

/0.5

MeV

p*(MC different contributions

p*(MC-FIT comparison

p* (K self-tag) p* (K self-tag)

p*(MC different contributions

We have two possible strategies to measure BR(0):1. 3 cut around the peak2. require 0 in EMC and use the obtained p* shape

The 2-cluster sample:

a) reproduces the p*() behavior but b) does not reproduce the p*(0) behavior at low and

high p* the fit overestimates 3-body decays and

contribution

1.1. 33 cut around the cut around the 00 peak peak

p* (K self-tag) p* (K self-tag)

Differences between p*(0)MC and p*(0)FIT

fractional difference fit_sel 0.0049 +/- 0.0001

fractional difference fit 0.02060+/- 0.0002

fractional difference fit 0.0208 +/- 0.0003

fractional difference fit_sel 0.0048 +/- 0.0001

Differences between p*()MC and p*()FIT

p* (K self-tag) p* (K self-tag)

The contribution under the 0 peak

fractional difference fit -0.00388 +/- 5.E-05fractional difference fit_sel -0.00059 +/- 2.-05

fractional difference fit -0.00413 +/- 6.E-05

fractional difference fit_sel -0.00055+/- 2.E-05

p* (K self-tag) p* (K self-tag)

Differences between p*(3-body)MC and p*(3-body)FIT

The 3-body contribution under the 0 peak

fractional difference fit -0.0288 +/- 0.0005fractional difference fit_sel -0.0160+/- 0.0004

fractional difference fit -0.0268+/- 0.0006fractional difference fit_sel -0.0154 +/- 0.0004

2.2. require require 0 0 in EMC and use the p* shapein EMC and use the p* shape

a) Check that 0 requirement does not introduce distortions

b) evaluate 0 reconstruction efficiency () with 0 tag sample

c) compare DATA to MC (can we use MC for Kl3 ?)

10 pb-1 0 tag sample

p*(0)TAG+

p*(0)MC

p* (K self-tag)

0 reconstruction efficiency (1)

plab_secondary pstar_secondary

0 reconstruction efficiency (2)

rvtx_2d rvtx_3d

Work in progress but the idea seems good

Exercise1: extract BR(0) and BR() from p*DATA

190 pb-1 DATA

********* BR results with munu tag********** ntag_munu = 13079285 npipi0 = 781313 ernpipi0 = 971.094 BR(pipi0) = 0.198226 +/- BR(pipi0) = 0.198226 +/- 0.0004424060.000442406 npipi0_fromsel = 832834 ernpipi0 = 971.094 BR(pipi0) fromsel = 0.211297 +/- BR(pipi0) fromsel = 0.211297 +/- 0.0005244390.000524439 nmunu = 2.49387E+06 ernmunu = 1619.88 BR(munu) = 0.604953 +/- BR(munu) = 0.604953 +/- 0.0007284810.000728481

There is a problem in the efficiencies……….There is a problem in the efficiencies……….

Exercise2: extract BR(0) and BR() from p*DATA

To use the efficiency evaluated directly from data require track to cluster association

10 pb-1

********* BR results with munu tag********** ntag_munu = 410065 npipi0 = 22945.7 ernpipi0 = 163.861 BR(pipi0) = 0.185681 +/- 0.00139935BR(pipi0) = 0.185681 +/- 0.00139935 npipi0_fromsel = 25180.7 ernpipi0 = 163.861 BR(pipi0) fromsel = 0.203767 +/- BR(pipi0) fromsel = 0.203767 +/- 0.001635080.00163508nmunu = 81280.8 ernmunu = 289.429BR(munu) = 0.628879 +/- 0.00252102BR(munu) = 0.628879 +/- 0.00252102********* BR results with pipi0 tag********** ntag_pipi0 = 312400 npipi0 = 16983.7 ernpipi0 = 146.819 BR(pipi0) = 0.182244 +/- 0.00181808BR(pipi0) = 0.182244 +/- 0.00181808 npipi0_fromsel = 18628.2 ernpipi0 = 146.819 BR(pipi0) fromsel = 0.19989 +/- BR(pipi0) fromsel = 0.19989 +/- 0.002039220.00203922nmunu = 61468.3 ernmunu = 252.179 BR(munu) = 0.627028 +/- 0.00380777BR(munu) = 0.627028 +/- 0.00380777

from2cluster

from and shift (MC

MC

190 pb-1

Exercise0 : extract BR(0) and BR() from p*MC

********* BR results with munu tag********** ntag_munu = 6530745 npipi0 = 433366 ernpipi0 = 3314.73 BR(pipi0) = 0.202514 +/- 0.00157059 npipi0_fromsel = 455826 ernpipi0 = 3314.73 BR(pipi0) fromsel = 0.21301 +/- 0.000478008 nmunu = 1443008 ernmunu = 1556.9 BR(munu) = 0.647016 +/- 0.000860994