Report on Report on 00 decay width:decay width:

analysis updatesanalysis updates

Analysis updates:Analysis updates: Clock frequency correction . Flux is ~2.4% Clock frequency correction . Flux is ~2.4%

upup

Tagger energy corrections were Tagger energy corrections were introducedintroduced

More statistics added: 130nA and 110nA More statistics added: 130nA and 110nA runs were added to previously used 100nA runs were added to previously used 100nA runs. Statistics increased by factor of 2 runs. Statistics increased by factor of 2 and stat. err dropped from 0.28eV to and stat. err dropped from 0.28eV to 0.18eV0.18eV

Analysis updates:Analysis updates:

Error budget was updatedError budget was updated

Efficiency was recalculated (non-resonant Efficiency was recalculated (non-resonant background was added) background was added)

Background from Background from and and ±± decays was decays was subtracted from subtracted from 00 yield yield

To make sure that skim data are not To make sure that skim data are not biased, raw data files were analyzed. biased, raw data files were analyzed. 00 yield fit parameters including lifetime are yield fit parameters including lifetime are stablestable

Response function of Hycal:Response function of Hycal:

What do we measure during snake scan ? Shape of experimentally observed response function:

*) resp. function itself*) accidentals (with false Tagger hits)*) electronics noise*) “leakage”

Observed elasticity (i.e. EObserved elasticity (i.e. EHycalHycal/E/ETAGGERTAGGER ratio) during snake scan when beam was ratio) during snake scan when beam was

centered on W2016centered on W2016

How to distinguish (tail and How to distinguish (tail and zero) of response function zero) of response function from the background. (Can from the background. (Can we do it in the future run to we do it in the future run to decrease our systematics ?)decrease our systematics ?)Put TAC behind Hycal during snake scanPut TAC behind Hycal during snake scan

Response function (MC) Response function (MC) with and w/o TAC during with and w/o TAC during

snakesnake

TAC itself has energy resolution (MC) ~ 7%/E

Hycal only Hycal with TAC

To study response function To study response function it was split into elasticity it was split into elasticity

regions:regions:

X = min – 0.2

X = 0.2 – 0.5

X = 0.5 – 0.8

X = 0.8 – 0.9

Fraction of events in elasticity Fraction of events in elasticity tails was estimated for runs with tails was estimated for runs with

different beam current: 20, 30, 50, different beam current: 20, 30, 50, 60, 95 pA60, 95 pA

Asymptotic values fromthe following simple fitwere used as a most close to the real values:

Y = c1/x + c0

Hycal resp. function itselfis assumed to be independent from beam current.

What does MC reproduce What does MC reproduce for response function:for response function:

Centered beamSnake scan

Data VS MC (percentage of Data VS MC (percentage of events in the tail of events in the tail of response function):response function):

X rangeX range MCMC Data Data (asympt.(asympt.))

Min – 0.2Min – 0.2 0.02 ± 0.02 ± 0.000.00

0.15 ± 0.15 ± 0.030.03

0.2 – 0.50.2 – 0.5 0.02 ± 0.02 ± 0.000.00

0.23 ± 0.23 ± 0.040.04

0.5 – 0.80.5 – 0.8 0.07 ± 0.07 ± 0.010.01

0.40 ± 0.40 ± 0.050.05

0.8 – 0.90.8 – 0.9 0.38 ± 0.38 ± 0.020.02

0.61 ± 0.61 ± 0.050.05

X rangeX range MCMC Data Data (asympt.(asympt.))

Min – Min – 0.20.2

0.03 ± 0.03 ± 0.010.01

0.06 ± 0.06 ± 0.020.02

0.2 – 0.50.2 – 0.5 0.02 ± 0.02 ± 0.000.00

0.14 ± 0.14 ± 0.040.04

0.5 – 0.80.5 – 0.8 0.08 ± 0.08 ± 0.010.01

0.26 ± 0.26 ± 0.030.03

0.8 – 0.90.8 – 0.9 0.40 ± 0.40 ± 0.020.02

0.57 ± 0.57 ± 0.040.04

1.3GeV 4.4GeV

Difference between data and MC ~ 0.5 – 0.9%

Snake scan data might Snake scan data might be used as a unique be used as a unique

measure of wrapping measure of wrapping thickness between thickness between

modules.modules.Any other measurements Any other measurements of this thickness could of this thickness could

not have enough not have enough accuracy.accuracy.

Tail of response function Tail of response function comes mostly from comes mostly from

wrapping:wrapping:

““tagging ratio” during tagging ratio” during snake, MC:snake, MC:

edges / wrapping edges / wrapping

“tagging ratio” means number of events with enough energy and position close to beam impact point divided by number of total events with normal beam

Elasticity cut 0.4 Elasticity cut 0.7

““tagging ratio” during tagging ratio” during snake, data:snake, data:

Elasticity cut 0.4

Elasticity cut 0.7

edges / wrapping

Dips near edges may slightlyvary from one module to another

Estimated contribution Estimated contribution from response function to from response function to

error budgeterror budget Systematic error comes from inconsistency Systematic error comes from inconsistency

between data and MC response functions between data and MC response functions (not from response function shape itself). (not from response function shape itself).

Since MC may underestimate tails of Since MC may underestimate tails of response function up to 0.9%, we have to response function up to 0.9%, we have to introduce correction factor of introduce correction factor of 0.9950.995 for for MC efficiency and MC efficiency and 0.5%0.5% sys. error comes sys. error comes from this item.from this item.

More precise measurement of Hycal More precise measurement of Hycal response function would decrease this response function would decrease this uncertaintyuncertainty

Lifetime sensitivity to Lifetime sensitivity to single gamma energy cut single gamma energy cut

valuevalue

Method 1: we have to vary cut value and check how result (with no additional correction for efficiency) depends on it.10% variation from cut value (0.5GeV) was used as a probe.This cut variation is changing result by 0.2%

Use

d c

ut

Cu

t va

riat

ion

Method 2: vary cut value and check how result (with corrected efficiency) depends on it.Final result shows 0.2% fluctuations from the mean value (it is probably statistical only fluctuations)

Lifetime sensitivity to Lifetime sensitivity to single gamma energy cut single gamma energy cut

valuevalue

Conclusion:Conclusion:

error budget contribution error budget contribution from this item is from this item is 0.2%0.2%

Lifetime sensitivity to Lifetime sensitivity to single gamma energy cut single gamma energy cut

valuevalue

Contribution from Contribution from misalignment:misalignment:

Beam VS Hycal position uncertainty: Beam VS Hycal position uncertainty: 0.2mm uncertainty value gives negligible 0.2mm uncertainty value gives negligible syst. Errorsyst. Error

Beam slope stability: Beam slope stability: 0.12mrad 0.12mrad uncertainty value gives syst. error uncertainty value gives syst. error 0.1%0.1%

Beam width stability: Beam width stability: varying beam varying beam parameters according to superharp scan parameters according to superharp scan data gives 0.3% syst. errordata gives 0.3% syst. error

Hycal Z uncertainty: Hycal Z uncertainty: 1.5cm uncertainty 1.5cm uncertainty value gives 0.4% syst. errorvalue gives 0.4% syst. error

and and ±±

sources of sources of 00 background were background were

subtractedsubtracted

The following sources of The following sources of quasielastic quasielastic s were s were

studied:studied: Coherent Coherent : : A -> A -> A A Incoherent Incoherent : : A -> A -> N A’ N A’

A -> A -> A’ A’ Incoherent Incoherent ±±: : A -> A -> ±± N A’ N A’

A -> A -> ±± A’ A’

With consequent decays:With consequent decays:

-> -> ; ; -> -> -- ++; ; ±± -> -> ±±

Simulations:Simulations:t’ distributions for t’ distributions for and and

production used production used

t’ = |t – tmin|

Simulations:Simulations:production angle production angle

distributions for distributions for and and usedused

Simulations:Simulations:cos(cos(GJGJ) distributions for ) distributions for

and and used used

1+x2

1-x2

Distributions obtained from MC were Distributions obtained from MC were scaled and subtracted from the datascaled and subtracted from the data

Scale factor for MC:Scale factor for MC:

KKscalescale = F = F data data / F/ FMCMC

FFMCMC = N = Nevent NCevent NC / ( / (L Br L Br ))

LL – number of atoms per sq. unit – number of atoms per sq. unitBrBr – decay branching ratio – decay branching ratio – – production cross sectionproduction cross section

00 elasticity distribution observed elasticity distribution observed (crystal part of Hycal) with (crystal part of Hycal) with

simulated background from simulated background from and and

and + -

contribution

+ - onlycontribution

00 elasticity distribution with elasticity distribution with subtracted background from subtracted background from and and

Elastic peakparametersimproved

dN/ddN/d for original data and with for original data and with background subtraction (on the background subtraction (on the

level of level of invariant mass invariant mass spectrum, bin by bin basis)spectrum, bin by bin basis)

rad. width changesby ~ -0.8%;more calculationswill be performed

original

Subtracted part

Non-resonant 2Non-resonant 2 background was added to background was added to

the MCthe MC Old method: number of reconstructed Old method: number of reconstructed 00 events events

was calculated in mass windowwas calculated in mass window New method: background with linear shape and New method: background with linear shape and

line parameters obtained from the data line parameters obtained from the data (individually for each T-counter and each (individually for each T-counter and each -bin) -bin) was added to MC distributions and the same was added to MC distributions and the same fitting procedure was performed as for the datafitting procedure was performed as for the data

MC data

Non-resonant 2Non-resonant 2 background affects on background affects on

efficiencyefficiencyNew efficiency curve

for 5.2GeVDifference between new

and old efficiencies

Rad. Width goes +1%

New formfactors (with more New formfactors (with more advanced calculations) were advanced calculations) were

introduced into analysisintroduced into analysis

Imaginary part of Imaginary part of formfactors were formfactors were

introduced:introduced:

dd/d/d interference = interference =

[ cos([ cos()· ( Re(Prim)· Re(Coh) + Im(Prim))· ( Re(Prim)· Re(Coh) + Im(Prim)· · Im(Coh) Im(Coh) ) +sin() +sin() ) · ( · ( Re(Prim) · Im(Coh) + Im(Prim)Re(Prim) · Im(Coh) + Im(Prim)· · Re(Coh) ) ]Re(Coh) ) ]

Interference term was modified: sin() appeared

Reanalyzing lifetime with Reanalyzing lifetime with all corrections applied:all corrections applied:

Old formfactors:(Primakoff region (0o-0.5o) 2 = 1.12

New formfactors:(Primakoff region (0o-0.5o) 2 = 1.05

22 was estimated for Primakoff region (0 was estimated for Primakoff region (0oo…0.5…0.5oo) ) separately to make sure quality of the fit in most separately to make sure quality of the fit in most

sensitive region.sensitive region.

Better agreement

Error budget tableError budget table Target (thickness and density) ……...Target (thickness and density) ……... ………. 0.1%………. 0.1% Target material (impurity) …………...Target material (impurity) …………... ………. -0.4%………. -0.4% Photon beam flux …………………….Photon beam flux ……………………. ……… 1.1%……… 1.1% Trigger efficiency ……………………... Trigger efficiency ……………………... ………. +0.1%………. +0.1% ADC channels status during run timeADC channels status during run time ………. negligible………. negligible Photon beam energy uncertaintyPhoton beam energy uncertainty ……..... 0.3%……..... 0.3% Photon beam flux distribution within E-countersPhoton beam flux distribution within E-counters

……………………... ……………………... ….…… 0.1%….…… 0.1% 00 branching ratio …………………….. branching ratio …………………….. ………. Negligible………. Negligible Energy cut for single Energy cut for single ………………..……………….. ………. 0.2%………. 0.2% Energy cut for Energy cut for 00 ……………………... ……………………... ………. negligible………. negligible 00 production angle resolution uncertainty production angle resolution uncertainty ………. 0.25%………. 0.25%

Error budget tableError budget table MC eff. simulations (statistical) accuracy ……MC eff. simulations (statistical) accuracy …… 0.3% 0.3% Selection of “best in time” beam candidates ..Selection of “best in time” beam candidates .. 0.3% 0.3% Hycal z uncertaintyHycal z uncertainty ……………................ ……………................ 0.4% 0.4% Beam position uncertainty ……….......................Beam position uncertainty ………....................... negligiblenegligible Beam direction uncertainty ……….....................Beam direction uncertainty ………..................... +0.1%+0.1% Beam divergence uncertainty ………..................Beam divergence uncertainty ……….................. 0.3%0.3% Timing cut (Timing cut (tdifftdiff)) ………................………................ 1.0%1.0% Hycal response functionHycal response function ………................ ………................ 0.5%0.5% Background separation: (Background separation: (currently used valuecurrently used value) .) .

1.0%1.0% Uncertainty in theoretical parametersUncertainty in theoretical parameters ……….………. ??

SummarySummary

Sources of background were taken Sources of background were taken into account (most of them)into account (most of them)

Error budget is close to be Error budget is close to be completedcompleted

Rad. width (to be updated):Rad. width (to be updated):

8.18eV ± 2.2% stat. ± 2.1% 8.18eV ± 2.2% stat. ± 2.1% syst.syst.

Plans:Plans: Update incoherent amplitude:Update incoherent amplitude:

dd/d/dshape updateshape update Include Fermi motionInclude Fermi motion (production angle and energy spread) ?(production angle and energy spread) ? Introduce different efficiency for Introduce different efficiency for

primakoff /coherent and incoherent primakoff /coherent and incoherent productionproduction

Check lifetime stability to variations of Check lifetime stability to variations of formfactor parameters. More formfactor formfactor parameters. More formfactor updates will be performed by Sergeyupdates will be performed by Sergey

Use of LG part of Hycal for better Use of LG part of Hycal for better incoherent estimationincoherent estimation

Spare slidesSpare slides

Fermi motion angular Fermi motion angular smearingsmearing

((00 production ): production ):

dw/dp (Carbon) Simulated smearing for = 0.25o, 1o and 2o