1. NSTAR 2013 Workshop Peñiscola, Valencian Community (Spain), May 27-30, 2013 I.G. Alekseev a,*, V.A. Andreev b, I.G. Bordyuzhin a, Ye.A. Filimonov b, V.V. Golubev b, A.B. Gridnev b, D.V. Kalinkin a, E.A. Konovalova b, L.I. Koroleva a, N.G. Kozlenko b, V.S. Kozlov b, A.G. Krivshich b, V.A. Kuznetsov b, B.V. Morozov a, V.M. Nesterov a, D.V. Novinsky b, V.V. Ryltsov a, M. Sadler c, M.M. Shestakova a, B.M. Shurygin a, P.S. Smirnov a, A.D. Sulimov a, V.V. Sumachev b, D.N. Svirida a, V.I. Tarakanov b, V.Yu. Trautman b 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 * igor.alekseev@itep.ru High precision measurements of the pion- proton differential elastic cross section in the second resonance region

2. Baryon anti-decuplet 2 ? Original prediction – N***(1710) From modified PWA – 1680 or 1730 1 1 ) R. Arndt et al., Phys.Rev. C69 (2004) 035208 NSTAR’2013 Igor Alekseev (ITEP, Moscow)

3. PDG 2012 3Igor Alekseev (ITEP, Moscow) NSTAR’2013

4. 4Igor Alekseev (ITEP, Moscow) Resonance parameters within safe reach by the experiment: This provides a good coverage of both theoretical and experimental expectations. and “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 step   p  K 0  :  REAC – 1% statistical precision and the same step  Very important data for PWA “Usual” resonace P11 N(1710)***  -polarization in the reaction   p  K 0  - an order of magnitude better precision then the best data available now - NIMROD (78) NSTAR’2013

5. Setup for elastic scattering 5Igor Alekseev (ITEP, Moscow)  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  p  p NSTAR’2013

6. 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. 7 Statistics so far 2.97 billion triggers P beam, MeV/c N trg, mln. Many thanks to ITEP accelerator! Igor Alekseev (ITEP, Moscow) NSTAR’2013

8. 8 Elastic events selection Hypothesis – pion scattered to the left arm θ цм =84 о The hypothesis is true The hypothesis is false Igor Alekseev (ITEP, Moscow) NSTAR’2013

9. Igor Alekseev (ITEP, Moscow)9 NSTAR’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. 5 o x 5 MeV/c bins

10. Igor Alekseev (ITEP, Moscow)10 NSTAR’2013 Bird’s eye view:  + p preliminary Statistical errors only. No correction for beam content. 2 o x ≈5 MeV/c bins

11. 11 NSTAR’2013  + p angle dependence Statistical errors only. No correction for beam content.

12. Igor Alekseev (ITEP, Moscow)12 NSTAR’2013  + p momentum dependence Statistical errors only. No correction for beam content. NSTAR’2013

13. Resonances and channel thresholds in the differential cross section Resonance influence on the cross section Other channel threshold influence on the cross section π - p→K 0 Σ 0 – M inv =1690.2 MeV P beam = 1033 MeV/c π - p→K + Σ - – M inv =1691.1 MeV P beam = 1035 MeV/c π - p→ωn – M inv =1722.3 MeV P beam = 1092 MeV/c π + p→K + Σ + – M inv =1683.1 MeV P beam = 1021 MeV/c S-wave only Any wave N(1685) – M inv =1685 МэВ → P beam = 1024 MeV/c Energy 13Igor Alekseev (ITEP, Moscow) A.I. Baz, ZETF 33 (1957) 923 NSTAR’2013

14. 14Igor Alekseev (ITEP, Moscow) Preliminary Statistical errors only. No correction for beam content. NSTAR’2013 Breight-Wigner resonance with Г=6 МэВ, Г el /Г = 0.05 θ CM =47.5 o θ CM =52.5 o θ CM =57.5 o θ CM =62.5 o

15. –pK0S +––p–pK0S +––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 15Igor Alekseev (ITEP, Moscow) New small time-projection chamber with GEM readout New neutron counter  – p  +  – n,  + p  +  + n … NSTAR’2013

16. 16Igor Alekseev (ITEP, Moscow) The new wide-apperture drift chamber tests at PNPI NSTAR’2013

17. Status and plans 17Igor Alekseev (ITEP, Moscow) 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 P beam =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. K 0 Λ-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