Обзор совещания по узким нуклонным резонансам NNR2009 Эдинбург, 8-11 июня 2009 года 25 докладов и 13 постеров Игорь Алексеев Семинар ИТЭФ, Москва 10 февраля 2010 года Narrow Nucleon Resonances: Predictions, Evidences, Perspectives

S C O P E The first statement on possible existence of a narrow nucleon resonance near 1680 MeV was based on the π Ν Partial Wave Analysis, though it suggested very small coupling with the π Ν channel. Then direct experimental evidences for the narrow bump in this mass area have been reported in the η photoproduction by three independent groups, first by GRAAL, and somewhat later by CB-ELSA and LNS. The resonance interpretation imply unfamiliar features: a small total width (< 25 MeV), very small π Ν coupling, and strong isotopic asymmetry of photocoupling (production off neutron at least an order higher than off proton). These properties are very similar to those predicted for the non- strange member of the exotic anti-decuplet. Alternative explanations of the observed bumps in terms of interference of known nucleon resonance have been suggested as well. It seems that, despite intensive studies of baryon spectroscopy world wide, we may have earlier missed a narrow nucleon resonance with mass around MeV. Therefore, the situation is worth a profound discussion, which may clarify the present status and suggest new directions for both experimental and theoretical investigations. D I S C U S S I O N Q U E S T I O N S Can the familiar physics (without narrow baryons) suggest a consistent fit to recently observed structures in γN→ηN? Do we have any reasons to expect narrow (i.e., Γ<ΓΔ) non-strange baryonic states (Nucleon- or Delta-like) having non-exotic nature? Could we consider any other reactions (different from γN→ηN) to look for such narrow non- strange baryon? Do we need exotica (baryonic and/or mesonic), or Why we are looking for it? Could we leave exotica alone and forget about it? Might exotica, if it exists, require revising the constituent quark model? May the Chiral Soliton Approach present an adequate model for complete QCD description of baryons? N(1685) ? ? ?

Graal Сечение с жестким симметричным обрезанием по недостающей массе MM(  n,  )

Упругое  0 p



?

ELSA

MAMI arXiv: [nucl-ex]

γp →  0 p MAMI

γp →  p MAMI C x ~-Re(H  H *  +H  H *  ) S11(1535) P11

Узкая особенность наблюдается: –f d  /d  γn→ηn (GRAAL, ELSA, MAMI, LNS) –f d  /d  γn→ γn (GRAAL) –  γp→ηp, γn →  0 n (  GRAAL -CLAS -MAMI) Не наблюдается: –d  /d  γp → X (GRAAL, CLAS, etc) –d  /d  γn →  n (GRAAL, LNS, etc) –C x γn →  0 n (MAMI) –  γp →  0 p (ELSA)

p min – минимальный возможный импульс спектатора MC

 (1520)  pK -  +  nK +

I.G. Alekseev (ITEP) EPECUR Search for narrow pion-proton states in s-channel at EPECUR: experiment status. I,G. Alekseev, I.G. Bordyuzhin, P.Ye. Budkovsky, D.A. Fedin, V.P. Kanavets, L.I. Koroleva, B.V. Morozov, V.M. Nesterov, V.V. Ryltsov, D.N. Svirida, A.D. Sulimov ITEP, Moscow V.A. Andreev, Ye.A. Filimonov, V.V. Golubev, A.I. Kovalev, N.G. Kozlenko, V.S. Kozlov, A.G. Krivshich, D.V. Novinsky, V.V. Sumachev, V.I. Tarakanov, V.Yu. Trautman PNPI, Gatchina M. Sadler ACU, Abilene

I.G Alekseev (ITEP) What is special in our experiment: “Formation”–type experiment. Extremely high invariant mass resolution (~0.6 MeV), provided by high momentum resolution of the magneto-optic channel 0.1%. Magnetless spectrometer with drift chambers. Liquid hydrogen target. Very small amount of matter on the particle paths. High statistical precision: 0.5% for elastic scattering and 1% for K  -production. and Not only pentaquark… 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)

I.G Alekseev (ITEP) Expected results Resonance parameters within safe reach by the experiment: This provides a good coverage of both theoretical and experimental expectations. Important note for the setup to be created The event selection in our magnetless spectrometer is based on the angular correlations of relatively low energy particles. This requires to have the smallest possible multiple scattering on the paths of all particles.  We needed light chambers with small amount of matter. Drift chambers with hexagonal structure were selected. Important note for the setup to be created The event selection in our magnetless spectrometer is based on the angular correlations of relatively low energy particles. This requires to have the smallest possible multiple scattering on the paths of all particles.  We needed light chambers with small amount of matter. Drift chambers with hexagonal structure were selected.

I.G Alekseev (ITEP) Setup for elastic scattering  Proportional chambers with 1mm pitch and 40 um aluminum foil potential electrode in the first focus (PC1-3) and in front of the target (PC4-6).  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 and hodoscopes H2, H3.  NMR system for measurement field in the magneto-optic channel dipoles with precision better 0.1%.  Time-of-flight difference between beam pions and antiprotons measurement to control average momentum in each bin.  2  10 7 elastic events in 2-3 weeks  – p  – p

I.G Alekseev (ITEP) Setup for  – p  K 0 S   +  –  – p  The same: 1.The beam line. 2.Beam proportional chambers. 3.The liquid hydrogen target. 4.Drift chambers DC1-5 with sencitive volume 800x1200 mm 2  To get reasonable 15-20% acceptance we need nearly 4  setup  Internal drift chambers DC6—DC9 (500х700 mm 2 )  Large drift chamber DC10 (1400х2000 мм 2 )  Double layer trigger and TOF hodoscope H1,2 with 100х100 mm 2 granularity  3  10 6 events in 4-5 weeks. 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

I.G Alekseev (ITEP) A prototype chamber with one coordinate and 2 mm pitch. The beam Two coordinate chambers with 1 mm pitch. Magnetic quadruple Proportional chambers with 1 mm pitch Manufactured and tested: 6 two-coordinate chambers 200х200 mm 40 um aluminum foil was used for potential electrodes Magic gas mixture 3200 channels of front-end electronics 100-channel front-end board, including signal amplification and shaping, digital delay line, trigger block recording and sending via USB 2.0 interface Test with  -source Proportional chambers in the first focus of the magneto-optic channel

I.G Alekseev (ITEP) Elastic scattering The first excitation level The second and the third excitation levels Horizontal coordinate distribution of events of internal accelerator beam scattering on the thin beryllium target. Events were collected at the beginning of spill. This picture corresponds to the momentum resolution 0.06%. Measurement of the beam momentum resolution P + 7 Be  P + 7 Be*

I.G Alekseev (ITEP) Liquid hydrogen target Liquid level Liquid hydrogen The mylar container L=25 cm,  40 mm. Beryllium outer shell Tested with liquid neon and hydrogen. LqHe Heat exchange block mylar container Н2Н2 liquid gas While filling with hydrogen Mylar container Pion beam Lq H 2 IN H 2 Gas OUT

I.G Alekseev (ITEP) Front-end electronics: 6 24-channel boards Drift chamber module “X” (wires along the short side) under test at ITEP accelerator. A “Y” module could be seen behind the “X” module. Drift chambers with hexagonal structure 0 1 м 0.5 м The beam Efficiency > 99% Precision  < 0.2 mm

Электроника Nucl.Instrum.Meth. A578 (2007) Система способна принимать более 100 тыс. триггеров за цикл ускорителя

Платы Цифровая задержка Программируемая длина Платы для пропорциональных камер: 100 каналов малошумящий трансимпедансный усилитель программируемый порог рабочая частота 96 МГц цифровая задержка мертвое время 200 нс передача данных по USB 2.0 размер платы 270х120 мм 2 выделяемая мощность 18 Вт Платы для дрейфовых камер: 24 канала малошумящий трансимпедансный усилитель программируемый порог эффективная частота оцифровки времени 576 МГц мертвое время 1500 нс передача данных по USB 2.0 размер платы 300х50 мм 2 выделяемая мощность 5.5 Вт измерение температуры

FPGACPU USB 2.0 Питание и триггер Платы Входы Усилители Компараторы

I.G Alekseev (ITEP) 43 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

I.G Alekseev (ITEP) Elastic events selection Correct pion and proton assignment Incorrect pion and proton assignment Extremely preliminary

I.G Alekseev (ITEP) The first physics run - spring weeks of beam time with pion beam 1 st week – setup 2 nd week – acquire statistics >500 millions triggers written  ~4-5 millions elastic events Pion beam momentum range 940 – 1135 MeV/c  invariant mass range 1640 – 1745 MeV As a conclusion: Elastic scattering: We have started taking data. We will have a calibration runs June and December We hope to continue data taking this year/ We need for K  -production: Trigger hodoscope with time-of-flight capability. ADC and TDC for this hodoscope. Large (~2400  1600 mm 2 ) drift chambers. New collaborators are WELCOME !