v.l. kashevarov. crystal ball@mami collaboration meeting, dubrovnik, 7-9 april 2008

V.L. Kashevarov. Crystal Ball@MAMI Collaboration Meeting, Dubrovnik, 7-9 April 2008

Photoproduction of Photoproduction of pairs on the pairs on the protonproton

► MotivationMotivation► Data analysisData analysis - overview- overview - timing- timing - identification of - identification of p p →→ oo p p reactionreaction - tagging efficiency- tagging efficiency► ResultsResults - overview- overview - total cross section- total cross section - invariant mass spectra- invariant mass spectra - angular distributions- angular distributions► SummarySummary


CB@ELSA GRAAL

J. Ajaka et al. J. Ajaka et al. PRL, 100, 052003 (2008), 100, 052003 (2008)Horn et al. Horn et al. arXiv:0711.1138.v1 [nucl-ex] (2007) [nucl-ex] (2007)The systematic error of The systematic error of ±±20% is not included 20% is not included

Data near threshold on the both pictures: T. Data near threshold on the both pictures: T. Nakabayashi et al. PR, C74, 035202 (2006) et al. PR, C74, 035202 (2006)

M. Doring, E. Oset, and D. Strotmann, PR, C73, 045209 (2006)M. Doring, E. Oset, and D. Strotmann, PR, C73, 045209 (2006)

MotivationMotivation

pp →→ D33D33 → → P33 P33

Hatched band: Hatched band: uncertainty of uncertainty of pp(1700) coupling(1700) coupling



a-f are Born terms, N* is S11(1535), (about 10% of the total cross section) a-f are Born terms, N* is S11(1535), (about 10% of the total cross section) g,f are resonance R in intermediate stateg,f are resonance R in intermediate state

A. Fix, M. Ostrick, and L. Tiator. EPJ, (2008) submitted, now is available in ArXiv


Canonical CMS for (N) Helicity CMS for (N)

(1900)S31 ** (1900)S31 ** (1920)P33 *** (1920)P33 *** (1930)D35 ***(1930)D35 ***(1910)P31 **** (1910)P31 **** (1700)D33 **** (1700)D33 **** (1905)F35 ****(1905)F35 ****


Examples: for J=1/2 resonances distribution overExamples: for J=1/2 resonances distribution over(HS) is uniform;(HS) is uniform; for J >1/2 resonances cosfor J >1/2 resonances cos depends on the ratio a =A depends on the ratio a =A3/23/2 /A /A1/2 1/2

and it is converx at a=1and it is converx at a=1

Obtaining experimental angular distributions for further theoretical interpretation is main goal of the presented work


- Beam time periods: 7-21 June 2007 and 10-25 July 2007- electron beam energy: 1508 MeV- beam current: 12 nA (full target) or 25 nA (empty target)- radiator: 10m Cu- diameter of collimator: 4 mm- target: LH2 (4.76 cm) - detectors: CB, PID, TAPS- tagger channels: 1-224 (617-1402 MeV) for analysis are used channels from 1 upto 147 (932-1402 MeV)- trigger: M2+ and CB energy sum > 350 MeV

Total number of raw events selected to be analyzed June July full target 5.78∙108 (~197 h) 4.62∙108 (~160 h) empty target 1.37∙107 (~10 h) 8.37∙107 (~60 h) main criteria for event sorting out: lost synchronization, wrong scaler readout, detector problems

main analysis cuts: time, invariant mass, missing mass

Data analysis: overview

Tagger-PID time (ns)

Tagger TDC hits

Ch. 28

2829

1, 27, 167

21, 23, 97

212,217

The best channel (no 202) has FWHM ~ 1ns

Data analysis: timingData analysis: timing


Tagger-CB(photons) time (ns)

Tagger-PID time (ns)

FWHM 1.8 ns

FWHM 1.4 ns

Data analysis: timingData analysis: timing


ij MeV) vs kl(MeV)

4 photons,3 combinations cut c

ut


Data analysis: reaction identificationData analysis: reaction identification

p p → → oo p p



Blue - full target, black - empty target, green - difference, red - simulation

0.932-1 GeV GeV

1.0-1.1 GeV1.0-1.1 GeV

1.1-1.2 GeV GeV

1.3-1.4 GeV1.3-1.4 GeV

m mmp

MM cut

= 15 MeV

= 19 MeV

= 10 MeV

= 5 MeV

= 23 MeV

= 8.6 MeV

= 8.8 MeV

= 8.9 MeV

= 8.9 MeV

= 9.1 MeV

= 23 MeV

= 24 MeV

= 24 MeV

= 24 MeV

= 25 MeV

1.2-1.3 GeV GeV

MeV) vs 6(MeV)

8 photons,28 combinations cut minimization



p p → → oooo p p

V.L. Kashevarov, Crystal Ball@MAMI Collaboration Meeting, Dubrovnik, 7-9 April 2008

Data analysis: tagging efficiencyData analysis: tagging efficiency

Tagger channelTagger channel Tagger channelTagger channel

Taggin

g e

ffici

ency

Taggin

g e

ffici

ency

June runJune run July runJuly run

11764.dat – black11881.dat – red11884.dat – green11943.dat – blue11982.dat - yellow

12087.dat – black12183.dat – red12251.dat – green12305.dat – blue (empty)

V.L. Kashevarov, Crystal-Ball@MAMI Collaboration Meeting, Dubrovnik, 7-9 April 2008

Data analysis: tagging efficiencyData analysis: tagging efficiency

Number of scaler readoutNumber of scaler readout

P2/t

agg

er_

scalr

(224)

P2/t

agg

er_

scalr

(224)

July run

June run

± 5 %

± 5 %

Tagger Efficiency runs


Results: overviewResults: overview

Total number of good events after all cuts, subtraction Total number of good events after all cuts, subtraction of random coincidences and empty target contribution:of random coincidences and empty target contribution:

June run 230.500 June run 230.500 75.500 75.500

July run 187.700 July run 187.700 60.50060.500

July run without TAPS 136.000 July run without TAPS 136.000 21.70021.700

GRAAL 57.400GRAAL 57.400

CB@ELSA (0.93-2.5 GeV) 16.500CB@ELSA (0.93-2.5 GeV) 16.500

For total cross sections are used only July run data (both For total cross sections are used only July run data (both decay modes) decay modes)For angular distributions – June and July data ( For angular distributions – June and July data ( to to decay mode) decay mode)


Results: total cross sectionsResults: total cross sections

Photon energy (GeV)Photon energy (GeV)

Tota

l cr

oss

sect

ion (

Tota

l cr

oss

sect

ion ( b

)b)

open circles – Tohoku 06green – CB@ELSA 07blue – GRAAL 08black – this workred – this work (without TAPS)

p p → → oo pp

p p → → oo p pTotal cross section without Total cross section without TAPS are by ~25% lowerTAPS are by ~25% lower then GRAAL datathen GRAAL data

July run onlyJuly run onlyStatistical errors only Statistical errors only


0.932-1 GeV GeV

1.0-1.1 GeV1.0-1.1 GeV

1.1-1.2 GeV GeV

1.2-1.3 GeVGeV

1.3-1.4 GeV1.3-1.4 GeV

blue: experimentred: p +(1232)simulation green: p o S11(1535) simulation

Results: invariant mass spectraResults: invariant mass spectra

p p


Results: angular distributionsResults: angular distributions

1.2-1.3 GeV GeV

1.3-1.4 GeV GeV

Blue points: experiment

Red curves: best fit

coscos (HS) (HS) coscos (CS) (CS) (HS)(HS) (CS)(CS)

- data are correcteddata are corrected for the detector for the detector efficiencyefficiency- integral over each integral over each distributiondistribution equals to 1equals to 1

Photon decay amplitudes for Photon decay amplitudes for (1700) (1700) N N : : AA3/23/2 / A / A1/21/2 = 1.45 (PDG 0.82 = 1.45 (PDG 0.82±±0.2, Arndt-96 1.080.2, Arndt-96 1.08±±0.25)0.25)

Branching fractions for Branching fractions for (1700) decay modes: (1700) decay modes:(1232)(1232)2.2 %2.2 %(no PDG value)(no PDG value)SS1111(1535) (1535) 0.1 % (no PDG value) 0.1 % (no PDG value)


1.2-1.3 GeV GeV

1.3-1.4 GeV GeV


p p (GeV)

Blue points: experiment

Red curves: theory

- experimental data are corrected for the detector acceptance- experimental data are corrected for the detector acceptance- integral over each spectrum equals to 1- integral over each spectrum equals to 1

> New experimental data for the total cross section, the angular > New experimental data for the total cross section, the angular distributions and the invariant mass spectra have presented;distributions and the invariant mass spectra have presented;

> fit the data to Mainz-Tomsk model have resulted the following > fit the data to Mainz-Tomsk model have resulted the following parameters of the parameters of the (1700)D33 resonance:(1700)D33 resonance:

Things to do:Things to do:> estimate systematic errors;> estimate systematic errors;> evaluate uncertainties of the fit;> evaluate uncertainties of the fit;> verify absolute normalization of the total cross section by obtaining > verify absolute normalization of the total cross section by obtaining

the total cross section ofthe total cross section of p p → → o o o o p p


SummarySummary

relation for helicity photon decay amplitudes: relation for helicity photon decay amplitudes: AA3/23/2 / A / A1/21/2 = 1.45 = 1.45

branching fractions for the decay modes:branching fractions for the decay modes:(1232)(1232)2.2 %2.2 %SS1111(1535) (1535) 0.1 % 0.1 %

MeV)

Missing mass cut

p p → → ++ n n

–mn (MeV)


MeV)

Missing mass cut

p p → → ++oo n n

–mn (MeV)



0.932-1 GeV GeV

1.0-1.1 GeV1.0-1.1 GeV

1.1-1.2 GeV GeV

1.2-1.3 GeVGeV

1.3-1.4 GeV1.3-1.4 GeV

blue: experimentred: p +(1232)simulation green: p o S11(1535) simulation


p p

v.l. kashevarov. crystal ball@mami collaboration meeting, dubrovnik, 7-9 april 2008

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