MESON 2014 Workshop KRAKÓW, POLAND 29 th May - 3 rd June 2014 I.G. Alekseev a,*, V.A. Andreev b, I.G. Bordyuzhin a, Ye.A. Filimonov b, V.V. Golubev b,

MESON 2014 Workshop KRAKÓW, POLAND 29th May - 3rd June 2014

I.G. Alekseeva,*, V.A. Andreevb, I.G. Bordyuzhina, Ye.A. Filimonovb, V.V. Golubevb, A.B. Gridnevb, D.V. Kalinkina, 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, B.M. Shurygina, 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]

New high precision data on the differential cross sections of the

pion-proton elastic scattering

Baryon resonances

2MESON’2014

Igor Alekseev (ITEP, Moscow)

PDG 2012

QM – quark model - S. Capstick and W. Roberts, Phys. Rev. D49, 4570; D57, 4301; D58, 074011.

Up to an excitation energy 2.4 GeV, about 45 N states are predicted but only 19 have some experimental association, including one and two-star resonaces

Baryon anti-decuplet

3

? Original prediction – N***(1710)From modified PWA (R. Arndt et al. 2004) – 1680 or 1730

MESON’2014

Igor Alekseev (ITEP, Moscow)

N(1685) Photoproduction off neutron:

GRAAL, CBELSA/TAPS, CBMAMI/TAPS

NO signal off proton

4Igor Alekseev (ITEP, Moscow)

pp 0SKpand

We have a lot of new photoproduction data now, but the most of pion-nucleon scattering data was obtained ~30 years ago – new data required.

• 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.• Non-magnetic spectrometer with drift chambers.• Liquid hydrogen target.• Very small amount of matter on the particle paths.• “Formation” – type experiment.

EPECUR:

• Precise cross section measurements:±p ±p: d/d – 0.5% statistical precision and 1 MeV momentum binp K0: REAC – 1% statistical precision and the same bin

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)

MESON’2014

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

MESON’2014

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)MESON’2014

7

Statistics so far 3.15 billion triggers

Many thanks to ITEP accelerator!

Igor Alekseev (ITEP, Moscow)MESON’2014

All runs but April’09 are analyzed

8

Elastic events selectionHypothesis – pion scattered to the left arm

θцм=84о

The hypothesis is true

The hypothesis is false

Igor Alekseev (ITEP, Moscow)MESON’2014

Igor Alekseev (ITEP, Moscow) 9MESON’2014

π-p – all data. Statistical errors only. No correction for beam content.


π+p – all data. Statistical errors only. No correction for beam content.

~9000 binsθCM=39-123o

Pbeam=820-1330 MeV/c~ 2% statistical errors

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

MESON’2014

Igor Alekseev (ITEP, Moscow) 12

Statistical errors only.No correction for beam content.

MESON’2014

2o x ≈5 MeV/c bins800-1330 MeV/c40-122o

black – our datablue – old data

π-p


Zoomed

Igor Alekseev (ITEP, Moscow) 14

Statistical errors only. No correction for beam content.

MESON’2014

π+p


Zoomed

–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 …

MESON’2014


New wide-apperture drift chambers:Two already manufactured and tested,One being assembled and the last in production.MESON’20

14

Wide-apperture drift chamber test at PNPI

Status and plans


Elastic scattering Detector EPECUR for precision measurement of elastic πp-scattering was built and commissioned. We took 4 physics runs and 3.15 billions of triggers are collected. Data analysis is on its way – 3 out of 4 runs are already processed. 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.

K0Λ-production 2 out of 4 required wide-aperture drift chambers are already manufactured and tested, one more is in the assembly stage and parts for the last one with horizontal wires are in production at PNPI. We have full front-end and DAQ electronic. We have all scintillator and 40% of PMTs for the TOF hodoscope. Assembly started.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.

We need the beam ! U10 (ITEP) – no solid plans of the accelerator reconstruction let alone time schedule U70 (Protvino) – there are plans, but no solid time schedule PS (CERN) - ???MESON’2014

Documents

MESON 2014 Workshop KRAKÓW, POLAND 29 th May - 3 rd June 2014 I.G. Alekseev a,*, V.A. Andreev b, I.G. Bordyuzhin a, Ye.A. Filimonov b, V.V. Golubev b,