Search for mesic nuclei in the photoproduction of and ' mesons - - PowerPoint PPT Presentation

▶
search for mesic nuclei in the photoproduction of and
SMART_READER_LITE
LIVE PREVIEW

Search for mesic nuclei in the photoproduction of and ' mesons - - PowerPoint PPT Presentation

Apr 22, 2023 50 likes •504 views

Search for mesic nuclei in the photoproduction of and ' mesons off light nuclei I.Keshelashvili Group of Prof. B. Krusche University of Basel Outline Outline Introduction Experimental Setup Data Analysis Results

slide-1
SLIDE 1

Search for mesic nuclei in the photoproduction of η and η' mesons

  • ff light nuclei

I.Keshelashvili Group of Prof. B. Krusche University of Basel

slide-2
SLIDE 2

University of Basel I.Keshelashvili FAIRNESS'13 [ 2]

Outline Outline

✔ Introduction ✔ Experimental Setup ✔ Data Analysis ✔ Results ✔ Conclusion

p p η p n p

γ

slide-3
SLIDE 3

University of Basel I.Keshelashvili FAIRNESS'13 [ 3]

Basel group EMC @ PANDA, PreAmp Basel group EMC @ PANDA, PreAmp & HV & HV

Low Noise/Low Power (LNP) preamplifier for APD and VPTT

  • W. Erni, M. Steinacher, I. Keshelashvili, B. Krusche

Cooled down to -25 oC

Material: PbW04 - 22 X0 Crystal size: 2 cm x 2 cm x 20 cm Energy resolution: 1.54% / √E/[GeV]+0.3% Number of crystals: 15552 Forward EMC: 3600 – Basel LNP Per crystal 2xAPD or VPTT

slide-4
SLIDE 4

University of Basel I.Keshelashvili FAIRNESS'13 [ 4]

L I N U X Apache/PHP/MySQL

ROOT based DAQ + slow control

FPGA Generator NIM - HV ISEG <10nA> Power Low V / I[nA]

VME - SADC Struck 12bit, 500MS/s

USB3 RS232 RS232 RS232 'APD'

2xCH

LNP PreAmp

Pulser Trigger 2xCH 1xCH

2014 Development Test setup Mass-production 2013

Basel group EMC @ PANDA, PreAmp Basel group EMC @ PANDA, PreAmp & HV & HV

slide-5
SLIDE 5

University of Basel I.Keshelashvili FAIRNESS'13 [ 5]

Introduction

slide-6
SLIDE 6

University of Basel I.Keshelashvili FAIRNESS'13 [ 6]

Strong Interaction Strong Interaction

η

ISI FSI

A A

slide-7
SLIDE 7

University of Basel I.Keshelashvili FAIRNESS'13 [ 7]

Why coherent production? Why coherent production?

1) Coherent 3) Incoherent (XS small) 2) Break-Up (main BG)

p p

η p n p γ

p n p

η n p p γ p

p n p

p n p η π0 γ

n p

p n p η γ n p n n

4) Double meson

slide-8
SLIDE 8

University of Basel I.Keshelashvili FAIRNESS'13 [ 8]

History History

1985: Bhalerao & Liu: coupled-channel analysis attractive s-wave η-A ; π−induced for A≥12

  • scatt. lengths: Re: 0.27-0.28 fm Im: 0.19-0.22 fm;

1986: Liu & Haider: suggestion of η-nucleus bound states for A>10 experiments: inconclusive evidence: Chrien et al. (1988): π+ +16O→p+ η15O Johnson et al. (1993): π+ +18O→π− + η18Ne Sokol et al. (99): γ +12C→p(n)+ η11B(C)→π++n+X 1993 - 2002: analysis of new η-production data from the proton: larger ηN-scattering lengths 1991 - 2002: T. Ueda, C. Wilkin, S.A. Rakityanski and others: suggestions of bound

2H-, 3H-, 3He-, 4He-η states

experiments: threshold behavior

  • f η-production
slide-9
SLIDE 9

University of Basel I.Keshelashvili FAIRNESS'13 [ 9]

  • η-photoproduction dominated by excitation of S11(1535)

→ spin-flip transition

  • Expectation for light nuclei:

I) 4He: J=0, I=0, isoscalar, non spin-flip → very small signal (not seen, only upper bounds, V. Hejny et al.) II) 2H: J=1, I=0, isoscalar, spin-flip → small signal (seen, almost in agreement with expectations) III) 3He: J=1/2, I=1/2, isovector, spin-flip → ‘large’ signal

Why is the Why is the η η-meson case special?

  • meson case special?
slide-10
SLIDE 10

University of Basel I.Keshelashvili FAIRNESS'13 [ 10]

TAPS - Photoproduction of TAPS - Photoproduction of η η – mesic – mesic 3

3He

He

Photoproduction of eta-mesic 3He

  • M. Pfeiffer at al. Phys. Rev. Lett. 92 (2004) 252001
slide-11
SLIDE 11

University of Basel I.Keshelashvili FAIRNESS'13 [ 11]

χ2/nfree=0.82 ANKE @ COSY, PRL 98, 242301

ANKE - Excitation function: dp→ ANKE - Excitation function: dp→3

3He

Heη η

p n p

p n p η

p p

p n p

slide-12
SLIDE 12

University of Basel I.Keshelashvili FAIRNESS'13 [ 12]

Experiment

slide-13
SLIDE 13

University of Basel I.Keshelashvili FAIRNESS'13 [ 13]

MAMI ( MAMI (Ma Mainzer inzer Mi Mikrotron) krotron)

continuous wave

slide-14
SLIDE 14

University of Basel I.Keshelashvili FAIRNESS'13 [ 14]

1m quadrupole radiator ~400MeV ~1.6GeV MAMI-C e- beam 352 Plastic Scintillators ∆E ~ 2-4MeV Crystal Ball Experiment

Glasgow Tagger Glasgow Tagger

slide-15
SLIDE 15

University of Basel I.Keshelashvili FAIRNESS'13 [ 15]

Photon Energy N

1/Eγ

Time (Tagger vs CB/TAPS) N

Real Events

I II Ee Ee' B Ee Εγ

Eγ=Ee-Ee' How to get the photon energy? How to get the photon energy?

slide-16
SLIDE 16

University of Basel I.Keshelashvili FAIRNESS'13 [ 16]

Crystal Ball / TAPS Detector Crystal Ball / TAPS Detector

Polarized Target

Crystal Ball 672 NaI(Tl) PID 24 Pl.Sci. TAPS BaF2 + PWO VETO 384 Pl.Sci.

slide-17
SLIDE 17

University of Basel I.Keshelashvili FAIRNESS'13 [ 17]

Crystal Ball detector at SPEAR @ SLAC Crystal Ball detector at SPEAR @ SLAC

✗

SPEAR began 1972

✗

e- e+ @ 3GeV

✗

J/ψ meson Nobel price 1976

✗

+many charmonium states

✗

SLAC, DASY, BNL, MAMI

slide-18
SLIDE 18

University of Basel I.Keshelashvili FAIRNESS'13 [ 18]

Crystal Ball / TAPS Detector Crystal Ball / TAPS Detector

TAPS BaF2 Invariant Mass Missing Energy or Mass Pulse Shape TOF – Time-Of-Flight

slide-19
SLIDE 19

University of Basel I.Keshelashvili FAIRNESS'13 [ 19]

Analysis

slide-20
SLIDE 20

University of Basel I.Keshelashvili FAIRNESS'13 [ 20]

Data Analysis Data Analysis

PID Scintillators TAPS Time TAPS - Tagger

slide-21
SLIDE 21

University of Basel I.Keshelashvili FAIRNESS'13 [ 21]

Results

γ+3He→3He+η

slide-22
SLIDE 22

University of Basel I.Keshelashvili FAIRNESS'13 [ 22]

p p η p n p

γ

slide-23
SLIDE 23

University of Basel I.Keshelashvili FAIRNESS'13 [ 23]

ME coherent η off 3He - 2γ (left) and 3π0/6γ (right)

Coherent Coherent η η photoproduction off photoproduction off 3

3He

He

slide-24
SLIDE 24

University of Basel I.Keshelashvili FAIRNESS'13 [ 24]

  • Sys. Err.

Coherent Coherent η η photoproduction off photoproduction off 3

3He

He

Shevchenko et al. 3N system in a microscopic few-body description. Strong dependence on the elastic ηN rescattering. Strong threshold effects, bad reproduction above the breakup threshold Fix et al. 3He and 3H in PWIA, in a distorted-wave impulse approximation (DWIA) using

  • ptical potential. Strong FSI effects. Underestimates XS.

Tiator et al. model was based on the PWIA. Strongly underestimates measured XS and does not reproduce the energy dependence.

slide-25
SLIDE 25

University of Basel I.Keshelashvili FAIRNESS'13 [ 25]

Coherent Coherent η η photoproduction off photoproduction off 3

3He

He

(Red) η→2γ decay (Blue) η→6γ decay The behavior of the angular distributions of the PWIA is dominated by the nuclear form factor, which is responsible for the strong forward peaking. Solid (dashed) curves: PWIA with realistic (isotropic) angular distribution for γ n →nη

slide-26
SLIDE 26

University of Basel I.Keshelashvili FAIRNESS'13 [ 26]

  • nucleon resonances produce opening angle dependent structures in excitation

functions

  • subtraction of excitation functions for different opening angles can produce

artificial structures almost everywhere

  • basically no hope to isolate tiny structure from η-mesic state in this

complicated landscape!

Photoproduction of Photoproduction of η η – mesic – mesic 3

3He

He

simulation of opening angle behavior for quasi-free π0 production and η-mesic state

slide-27
SLIDE 27

University of Basel I.Keshelashvili FAIRNESS'13 [ 27]

Photoproduction of Photoproduction of η η – mesic – mesic 3

3He

He

Excitation functions Excitation functions x Eγ

6

γ+3He→(η3He)→p+π0+X

slide-28
SLIDE 28

University of Basel I.Keshelashvili FAIRNESS'13 [ 28]

✗ Strong threshold enhancement and shape of angular distributions confirmed ✗ Evidence for very strong FSI effects ✗ Alternative decay channel π0-p back-to back suffers from complicated background structure, signal not confirmed

Summary I Summary I

γ+3He→3He+η

slide-29
SLIDE 29

University of Basel I.Keshelashvili FAIRNESS'13 [ 29]

Coherent η -photoproduction off

7Li nuclei

(Ph.D. work of Yasser Maghrbi)

slide-30
SLIDE 30

University of Basel I.Keshelashvili FAIRNESS'13 [ 30]

ME coherent η off 7Li - 2γ (left) and 3π0/6γ (right)

Coherent Coherent η η- photoproduction off

  • photoproduction off 7

7Li

Li

slide-31
SLIDE 31

University of Basel I.Keshelashvili FAIRNESS'13 [ 31]

Coherent Coherent η η- photoproduction off

  • photoproduction off 7

7Li

Li

slide-32
SLIDE 32

University of Basel I.Keshelashvili FAIRNESS'13 [ 32]

Coherent Coherent η η- photoproduction off

  • photoproduction off 7

7Li

Li

X

slide-33
SLIDE 33

University of Basel I.Keshelashvili FAIRNESS'13 [ 33]

Photoproduction of Photoproduction of η η – mesic – mesic 7

7Li

Li γ+7Li→(η7Li)→p+π0+X

slide-34
SLIDE 34

University of Basel I.Keshelashvili FAIRNESS'13 [ 34]

Coherent η′ -photoproduction off LD and 3He nuclei (Ph.D. work of Roman Trojer)

slide-35
SLIDE 35

University of Basel I.Keshelashvili FAIRNESS'13 [ 35]

Coherent Coherent η′ η′- photoproduction off

  • photoproduction off LD

LD γ+d→X+η′→X+η(γγ)π0(γγ)π0(γγ)

slide-36
SLIDE 36

University of Basel I.Keshelashvili FAIRNESS'13 [ 36]

γ+d→X+η′→X+η(γγ)π0(γγ)π0(γγ) Coherent Coherent η′ η′- photoproduction off

  • photoproduction off LD

LD

slide-37
SLIDE 37

University of Basel I.Keshelashvili FAIRNESS'13 [ 37]

Coherent Coherent η′ η′- photoproduction off

  • photoproduction off 3

3He

He γ+3He→X+η′→X+η(γγ)π0(γγ)π0(γγ)

slide-38
SLIDE 38

University of Basel I.Keshelashvili FAIRNESS'13 [ 38]

γ+3He→X+η′→X+η(γγ)π0(γγ)π0(γγ) Coherent Coherent η′ η′- photoproduction off

  • photoproduction off 3

3He

He

slide-39
SLIDE 39

University of Basel I.Keshelashvili FAIRNESS'13 [ 39]

✗ Similarities between 3He and 7Li cross section shows strong threshold enhancement ✗ 7Li decay channel π0-p back-to-back suffers from complicated background structure, signal not confirmed ✗ η' show also very rapid rise of the total cross section

Summary II Summary II

slide-40
SLIDE 40

University of Basel I.Keshelashvili FAIRNESS'13 [ 40]

Outlook Outlook

✗ We have accepted proposal by the PAC

p n p

p n p η π0 γ

slide-41
SLIDE 41

University of Basel I.Keshelashvili FAIRNESS'13 [ 41]

ηπ ηπ0

0- photoproduction off deuteron

  • photoproduction off deuteron
slide-42
SLIDE 42

University of Basel I.Keshelashvili FAIRNESS'13 [ 42]

ηπ ηπ0

0- photoproduction off deuteron

  • photoproduction off deuteron

Preliminary results: Ph.D. Work of A. Käser

slide-43
SLIDE 43

University of Basel I.Keshelashvili FAIRNESS'13 [ 43]

Thank you for your Attention

University of Basel Group of Prof. Bernd Krusche Group members

Manuel Dieterle | Stefanie Garni | Alexander Käser Irakli Keshelashvili | Markus Oberle | Tigran Rostomyan | Thomas Strub Dominik Werthmüller | Lilian Witthauer

slide-44
SLIDE 44

University of Basel I.Keshelashvili FAIRNESS'13 [ 44]

  • allows to investigate sequential decays
  • η works as isospin filter: Due to isospin conservation, only higher

energetic Ν∗(∆∗) resonances can can decay into a ηΝ∗(∆∗) intermediate state

ηπ ηπ0

0- photoproduction off deuteron

  • photoproduction off deuteron
slide-45
SLIDE 45

University of Basel I.Keshelashvili FAIRNESS'13 [ 45]

ηπ ηπ0

0- photoproduction off deuteron

  • photoproduction off deuteron