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SPIN 2012, Dubna, September 17-22, 2012

High precision measurements of the pion-proton elastic scattering and kaon-lambda production in the EPECUR experiment. I.G. Alekseev a,* , V.A. Andreev b , I.G. Bordyuzhin a , D.A. Fedin a , Ye.A. Filimonov b ,

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SPIN 2012, Dubna, September 17-22, 2012

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  1. High precision measurements of the pion-proton elastic scattering and kaon-lambda production in the EPECUR experiment 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 aInstitute for Theoretical and Experimental Physics, B. Cheremushkinskaya 25, Moscow, Russia. bPetersburg Nuclear Physics Institute, Gatchina, Leningrad district, Russia cAbilene Christian University, Abilene, Texas, USA * igor.alekseev@itep.ru SPIN 2012, Dubna, September 17-22, 2012

  2. Pentaquark antidecuplet Original prediction – N***(1710) From modified PWA – 1680 or 17301 ? 1) R. Arndt et al., Phys.Rev. C69 (2004) 035208 Igor Alekseev (ITEP, Moscow)

  3. N(1685) NNR’2009, Edinburg, June 8-10, 2009 http://2009physicsevents.org η-photoproduction off neutron GRAAL: Igor Alekseev (ITEP, Moscow)

  4. M.J Amaryan et al. Phys.Rev. C85 (2012) 035209 • 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 MCcor MC Igor Alekseev (ITEP, Moscow)

  5. S. Naohito @ SPIN 2010

  6. Resonance parameters within safe reach by the experiment: This provides a good coverage of both theoretical and experimental expectations. and EPECUR: • “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. Not narrow resonances only … • Precise cross section measurements: • p p: d/d –0.5% statistical precision and 1 MeV momentum step • p  K0: REAC–1% statistical precision and the same step •  Very important data for PWA • “Usual” resonaceP11 N(1710)*** • -polarizationin the reaction p  K0 - an order of magnitude better precision then the best data available now - NIMROD (78) Igor Alekseev (ITEP, Moscow)

  7. 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 pp Igor Alekseev (ITEP, Moscow)

  8. Engineering run (December 2008) 7 millions of triggers were written with the liquid hydrogen target Hodoscope Drift chambers Liquid hydrogen target heat exchanger Proportional chambers I.G Alekseev (ITEP) 8 Igor Alekseev (ITEP, Moscow)

  9. Statistics so far 2.97 billion triggers Ntrg, mln. Many thanks to ITEP accelerator! Pbeam, MeV/c Igor Alekseev (ITEP, Moscow)

  10. Elastic events selection Hypothesis – pion scattered to the left arm θцм=84о The hypothesis is false The hypothesis is true Igor Alekseev (ITEP, Moscow)

  11. Track reconstruction efficiency We require 3 hits on the track out of 4 possible in each projection 100% 99% Igor Alekseev (ITEP, Moscow)

  12. Corrected to the acceptance, efficiency and decays Preliminary Statistical errors only Igor Alekseev (ITEP, Moscow)

  13. Corrected to the acceptance, efficiency and decays Preliminary Statistical errors only Igor Alekseev (ITEP, Moscow)

  14. Corrected to the acceptance, efficiency and decays Preliminary Statistical errors only Igor Alekseev (ITEP, Moscow)

  15. Corrected to the acceptance, efficiency and decays Preliminary Statistical errors only Igor Alekseev (ITEP, Moscow)

  16. Resonances and channel thresholds in the differential cross section Resonance influence on the cross section Any wave Energy N(1685) – Minv=1685 МэВ → Pbeam= 1024MeV/c Other channel threshold influence on the cross section S-wave only A.I. Baz, ZETF 33 (1957) 923 π-p→K0Σ0– Minv=1690.2 MeVPbeam=1033 MeV/c π-p→K+Σ-– Minv=1691.1 MeVPbeam= 1035 MeV/c π-p→ωn – Minv=1722.3 MeVPbeam= 1092MeV/c π+p→K+Σ+ – Minv=1683.1 MeVPbeam= 1021 MeV/c Igor Alekseev (ITEP, Moscow)

  17. Preliminary Statistical errors only Igor Alekseev (ITEP, Moscow)

  18. Preliminary Statistical errors only Igor Alekseev (ITEP, Moscow)

  19. Statistical errors only Preliminary Igor Alekseev (ITEP, Moscow)

  20. Preliminary Statistical errors only • 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 Igor Alekseev (ITEP, Moscow)

  21. Statistical errors only Preliminary Igor Alekseev (ITEP, Moscow)

  22. Preliminary Statistical errors only Igor Alekseev (ITEP, Moscow)

  23. Preliminary Statistical errors only Igor Alekseev (ITEP, Moscow)

  24. Preliminary Statistical errors only Igor Alekseev (ITEP, Moscow)

  25. –pK0S +––p 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 We keep the target and the beam equipment The drift chambers we already have New wide-aperture drift chambers New hodoscopes Igor Alekseev (ITEP, Moscow)

  26. The new wide-apperture drift chamber tests at PNPI Igor Alekseev (ITEP, Moscow)

  27. 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 2.97billions 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. Igor Alekseev (ITEP, Moscow)

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