SPIN 2012, Dubna, September 17-22, 2012 I.G. Alekseev a,*, V.A. Andreev b, I.G. Bordyuzhin a, D.A. Fedin a, Ye.A. Filimonov b, V.V. Golubev b, A.B. Gridnev

SPIN 2012, Dubna, September 17-22, 2012

I.G. Alekseeva,*, V.A. Andreevb, I.G. Bordyuzhina, D.A. Fedina, Ye.A. Filimonovb, V.V. Golubevb, A.B. Gridnevb, E.A. Konovalovab, L.I. Korolevaa, N.G. Kozlenkob, V.S. Kozlovb, A.G. Krivshichb, B.V. Morozova, V.M. Nesterova, D.V. Novinskyb,

V.V. Ryltsova, M. Sadlerc, A.D. Sulimova, V.V. Sumachevb, D.N. Sviridaa, V.I. Tarakanovb, V.Yu. Trautmanb

a Institute for Theoretical and Experimental Physics, B. Cheremushkinskaya 25, Moscow, Russia. b Petersburg Nuclear Physics Institute, Gatchina, Leningrad district, Russia

c Abilene Christian University, Abilene, Texas, USA* [email protected]

High precision measurements of the pion-

proton elastic scattering and kaon-lambda

production in the EPECUR experiment

Pentaquark antidecuplet

2

?

Original prediction – N***(1710)From modified PWA – 1680 or 17301

1) R. Arndt et al., Phys.Rev. C69 (2004) 035208SPIN’2012

Igor Alekseev (ITEP, Moscow)

N(1685)

3

NNR’2009, Edinburg, June 8-10, 2009 http://2009physicsevents.org

η-photoproduction off neutron

GRAAL:

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4Igor Alekseev (ITEP, Moscow)

M.J Amaryan et al. Phys.Rev. C85 (2012) 035209

MC

MCcor

The same CLAS statistics of 2004 (g11a run period) as in R. De Vita et al., [CLAS Collaboration], Phys. Rev. D74, 032001 (2006) A narrow structure at KS missing mass MX(KS) = 1.543 GeV with a Gaussian width = 0.006 GeV for the reaction γp→pKSKL

when M(KSKL) = mϕ and −tΘ<0.45 GeV2 with 5.4σ statistical significance.

S+MCcor

S. Naohito @ SPIN 2010


Resonance parameters within safe reach by the experiment:

This provides a good coverage of both theoretical and experimental expectations.

Elastic scattering

K-production

Width (2-20) MeV (2-20) MeV Elastic width, Гel >0.1 MeV >0.02 MeV Elasticity, X >0.05 >0.01

pp 0SKpand

• “Formation” – type experiment.• Extremely high invariant mass resolution (~0.6 MeV), provided by high momentum resolution of the magneto-optic channel 0.1%.• High statistical precision: 0.5% for elastic scattering and 1% for K-production.• Magnetless spectrometer with drift chambers.• Liquid hydrogen target.• Very small amount of matter on the particle paths.

EPECUR:

Not narrow resonances only …• Precise cross section measurements:p p: d/d – 0.5% statistical precision and 1 MeV momentum stepp K0: REAC – 1% statistical precision and the same step

Very important data for PWA• “Usual” resonace P11 N(1710)***• -polarization in the reaction p K0 - an order of magnitude better precision then the best data available now - NIMROD (78)

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Setup for elastic scattering


Proportional chambers with 1mm pitch and 40 um aluminum foil potential electrode in the first focus (1FCH1-4) and in front of the target (2FCH1-4). Momentum of each incident pion is tagged with the precision better 0.1%. Liquid hydrogen target with beryllium outer shell and mylar hydrogen container. The target diameter is 40 mm and the length along the beam ~250 mm. 8 modules of drift chambers with hexagonal structure to measure tracks of particles produced. Trigger scintillation counters S1, S2, A1. NMR system for measurement field in the magneto-optic channel dipoles with precision better 0.1%. Triggers:

Main = S1∙1FCH ∙S2 ∙2FCH ∙(!A1)With prescale:Mom1F = S1∙1FCH ∙S2 ∙2FCH BeamPos = S1∙1FCH∙2FCH ∙ A1

pp

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I.G Alekseev (ITEP) 8

Drift chambers

Proportional chambers

Hodoscope

Liquid hydrogen target heat exchanger

Engineering run (December 2008)7 millions of triggers were written with the liquid

hydrogen target

8Igor Alekseev (ITEP, Moscow)SPIN’2012

9

0

10

20

30

40

50

6013

3013

1513

0012

8512

7012

5512

4012

2512

1011

9511

8011

6511

5011

3511

2011

0510

9010

7510

6010

4510

3010

1510

00 985

970

955

940

925

910

895

880

865

850

835

820

April 09 pi-, 453 mln. trg.April 10 pi-, 1250 mln. trg.June 10 pi+, 688 mln. trg.February 11 pi+, 275 mln. trg.February 11 pi-, 292 mln. trg.

Statistics so far 2.97 billion triggers

Pbeam, MeV/c

Many thanks to ITEP accelerator!

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10

Elastic events selectionHypothesis – pion scattered to the left arm

θцм=84о

The hypothesis is true

The hypothesis is false

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Track reconstruction efficiencyWe require 3 hits on the track out of 4 possible in each projection

100%

99%

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Preliminary

Corrected to the acceptance, efficiency and decays


Statistical errors only

Preliminary




Preliminary




Preliminary




Resonances and channel thresholds in the differential cross sectionResonance influence on the cross section

Other channel threshold influence on the cross section

π-p→K0Σ0 – Minv=1690.2 MeV Pbeam = 1033 MeV/cπ-p→K+Σ- – Minv=1691.1 MeV Pbeam = 1035 MeV/cπ-p→ωn – Minv=1722.3 MeV Pbeam = 1092 MeV/cπ+p→K+Σ+ – Minv=1683.1 MeV Pbeam = 1021 MeV/c

S-wave only

Any wave

N(1685) – Minv=1685 МэВ → Pbeam = 1024 MeV/cEnergy


A.I. Baz, ZETF 33 (1957) 923

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Some irregularity is seen in the region of the most interest (1020-1040 MeV) in several θCM bins

Only one half of the statistics in this region was already analyzed

We plan to get more statistics in the narrow energy range

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–pK0S +––p

We keep the target and the beam equipment

The drift chambers we already have

New wide-aperture drift chambers

New hodoscopes

Most of the events have either all 4 particles going forward or 3 particles including the proton going forward and one pion going in some other direction

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The new wide-apperture drift chamber tests at PNPI

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Status and plans


Elastic scattering Detector EPECUR for precision measurement of elastic πp-scattering was built and comissioned:

track efficiency in the drift chambers > 99% beam momentum tagging is better 0.1%

We took 4 physics runs and 2.97 billions of triggers are collected. The analysis is under way. The preliminary results show some irregularity at Pbeam=1020-1040 MeV/c. We plan to take more data in the narrow region of interest as well as extend the measurement till 2 GeV/c The beam composition will be determined using Cherenkov counter and Monte-Carlo simulations

K0Λ-production The first out of 4 required wide-aperture drift chambers is manufactured and is being tested at PNPI We have full front-end and DAQ electronic Engineering of mechanical structure as well as of TOF forward hodoscope is under way.

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Documents

SPIN 2012, Dubna, September 17-22, 2012 I.G. Alekseev a,*, V.A. Andreev b, I.G. Bordyuzhin a, D.A. Fedin a, Ye.A. Filimonov b, V.V. Golubev b, A.B. Gridnev