nstar 2013 workshop peñiscola, valencian community (spain), may 27-30, 2013 i.g. alekseev a,*, v.a....

NSTAR 2013 Workshop Peñiscola, Valencian Community (Spain), May 27-30, 2013

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

V.M. Nesterova, D.V. Novinskyb, V.V. Ryltsova, M. Sadlerc, M.M. Shestakovaa, B.M. Shurygina, P.S. Smirnova, 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 differential elastic cross section in

the second resonance region

Baryon anti-decuplet

2

?

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

1) R. Arndt et al., Phys.Rev. C69 (2004) 035208NSTAR’2013

Igor Alekseev (ITEP, Moscow)

PDG 2012

3Igor Alekseev (ITEP, Moscow)NSTAR’2013

4Igor Alekseev (ITEP, Moscow)

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) 6

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

6Igor Alekseev (ITEP, Moscow)NSTAR’2013

7

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!

Igor Alekseev (ITEP, Moscow)NSTAR’2013

8

Elastic events selectionHypothesis – pion scattered to the left arm

θцм=84о

The hypothesis is true

The hypothesis is false

Igor Alekseev (ITEP, Moscow)NSTAR’2013

Igor Alekseev (ITEP, Moscow) 9NSTAR’2013

Bird’s eye view: –p preliminary

baseline of the each next dataset is shifted by 0.4 mb/sr

Statistical errors only.No correction for beam content.

5o x 5 MeV/c bins


Bird’s eye view: +p preliminary Statistical errors only. No correction for beam content.

2o x ≈5 MeV/c bins

11NSTAR’2013

+p angle dependence Statistical errors only. No correction for beam content.


+p momentum dependence Statistical errors only. No correction for beam content.

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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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Statistical errors only.No correction for beam content.

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Breight-Wigner resonance with Г=6 МэВ, Гel/Г = 0.05

θCM=47.5o θCM=52.5o

θCM=57.5o θCM=62.5o

–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


New small time-projection chamber with GEM

readout

New neutron counter –p+–n, +p++n …

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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 commissioned. We took 4 physics runs and 2.97 billions of triggers are collected. The analysis is under way. The preliminary results show some irregularity in π-p-scattering at Pbeam=1020-1040 MeV/c. For 2012 we planed to take more data in the narrow region of interest as well as extend the measurement till 2 GeV/c and to determine the beam composition using Cherenkov counter. These plan was ruined by the conflagration at ITEP accelerator complex, as a result of which large portion of the accelerator electronics, vacuum pumps and cables was destroyed. Though injectors, rings, beam lines, main power supply and experiments were not directly affected by the fire, the recovery would take 3-5 years. We have to use Monte-Carlo only to get beam pollution by muons and electrons. Data analysis is on its way.

K0Λ-production The first out of 4 required wide-aperture drift chambers is manufactured and tested, two more are in the assembly stage and the one with horizontal wires is already designed at PNPI. We have full front-end and DAQ electronic. Engineering of mechanical structure as well as of TOF forward hodoscope is under way. The small TPC with GEM readout is in R&D stage. More distant plans include neutron counter to get access to the reactions with Δ-production.

NSTAR’2013

nstar 2013 workshop peñiscola, valencian community (spain), may 27-30, 2013 i.g. alekseev a,*, v.a....

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