Time Reversal Invariance in electromagnetic interactions

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Time Reversal Invariance in electromagnetic
interactions
Alessandra Fantoni INFN - Laboratori Nazionali di
Frascati

• Introduction
• Processes
• Experimental Situation
• Perspectives

International Workshop on Nucleon Form Factors,
LNF 12-14 Ottobre 2005
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Introduction 1-
Invariance of the laws of physics under discrete
symmetry operations reflect fundamental
properties of matter

• Not all processes are invariant under every
  simmetry operation
• weak interaction violates invariance under
  space reflection (parity P)
• decay of neutral K meson violates invariance
  under combined charge conjugation (C) and parity
  operations (CP)

For certain whether C, P and CP conserving
interactions are also invariant under time
reversal (T) NOT known !!!
T invariance is reflected in the law of
conservation of energy for systems with
conservative forces
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Introduction -2-
Fundamental theorem of relativistic field theory
All interactions must be invariant
under CPT operation
CP invariance T invariance CP violation
T violation
No direct tests of T invariance in CP conserving
interactions
Strong interaction Hh invariant under Ph, Th and
Ch
E.m. interaction Hg invariant under Pg, Tg and Cg
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Introduction -3-
Hh and Hg invariant under Ph Pg and CgPgTg
ChPhTh
For strong interacting particles no complete
theory of electromagnetic interaction exists
No evidence Hg invariant under Ch or Th

• Difficulty of detection Ch or Th violations
• electromagnetic effects well described by lowest
  order (Born approximation)
• Gauge invariance

Test for Th are challenging in electromagnetic
interactions of leptons with nucleons
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Processes
Literature Bernstein et al. PR139 (1965) 1650
Christ Lee PR143 (1966) 1310
Karpman et al PRL16 (1966) 633 Karpman et al.
PR174 (1968) 1957

• A ? 0
• violation of Th invariance
• higher order effects (a3) interference between
  1g and 2g amplitudes without requiring T
  invariance violation
• A(a3) small
• A(a3) charge dependent

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Experimental Situation -1-

• Cambridge J.R.Chen et al. PRL 21 (1968) 1279
• J.A.Appel et al. PRD 1 (1970) 1285

Inelastic scattering on h.e. e- from polarized
p Target 92 C2H5OH, 8 H20 PT22 E(e-) 4, 6
GeV I 3 nA
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Experimental Situation -1-

• Cambridge J.R.Chen et al. PRL 21 (1968) 1279
• J.A.Appel et al. PRD 1 (1970) 1285

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Experimental Situation -2-
b) SLAC S.Rock et al. PRL 24 (1970) 748
Target 95 butanol, 5 H20 PT35 E(e-) 15,
18 GeV Q2 0.4, 0.6, 1.0 E(e) 12 GeV Q2
0.4 e- , e but not covering same kinematic range
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Experimental Situation -2-
b) SLAC S.Rock et al. PRL 24 (1970) 748
Data everywhere consistent with A 0
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Experimental Situation -2-
b) SLAC S.Rock et al. PRL 24 (1970) 748
Data everywhere consistent with A 0
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Experimental Situation -3-

• Old data NOT very accurate
• Conclusions hard to extract
• Points still open for discussion
• Jlab LoI 01-002

• How to better investigate the problem ?
• What is needed?

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Perspectives -1-
e and e- in the same kinematic range Emin
(e/e-) 1.2 GeV (first resonance) Edes (e/e-)
3 GeV
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Perspectives -2-

• no FSI interaction (no hadron detected)
• detection of polarization vector of outgoing
  nucleon
• same case as before

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Perspectives -3-
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Perspectives inside LNF

• LNF is studying perspectives for the future
• Increase of energy of DAFNE
• Possibility to use upgraded DAFNE Linac

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Courtesy of SPARC/X Collaboration
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Courtesy of SPARC/X Collaboration
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Courtesy of SPARC/X Collaboration
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Courtesy of SPARC/X Collaboration
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Courtesy of SPARC/X Collaboration
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Courtesy of SPARC/X Collaboration
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Perspectives

• LNF is studying scenarios for near-mid-long range
• MIUR funds for SPARXino RD
• Proposal within beginning 2006 from SPARC/X
  Collaboration for Dafne Linac upgrade from 800
  MeV to 1.2-1.5 GeV
• Possibility to E1.8 GeV under study
• (new cavities 11 GHz instead of 3 GHz new
  technology for LNF)
• e beam available (PC)
• Possibility to use these beams for dedicated
  proposals
• such as Time invariance in em interaction
• Further developments depend on approval/decisions

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• Q 2 nC n 50 Hz L 20 ns
• lt I gt 100 mA at 50 Hz
• ltlt I gtgt 0.1 mA
• 102 times better than previous experiments
• Possibility 2nC -gt 10nC

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SPARC
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Conclusioni
HERMES primo esperimento che prova a separare
tutti i fattori che compongono lo spin del
nucleone