How to testCP, T, andCPT invariance in the three photon decay of polarized3 S 1 positronium

Bernreuther, W.; Rai, J P; Löw, U.; Nachtmann, Otto

doi:10.1007/bf01412589

Cited by 64 publications

(81 citation statements)

References 19 publications

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“…Thus the angular correlation is CP -odd and T odd but conserves CP T symmetry. This correlation would appear in general [10] when the CP -violating effect exists in Ps.…”

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confidence: 90%

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Search forCPViolation in Positronium Decay

et al. 2010

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CP -violation in the quark sector has been well established over the last decade, but has not been observed in the lepton sector. We search for CP -violating decay processes in positronium, using the angular correlation of ( S · k1)( S · k1 × k2), where S is the the positronium spin and k1, k2 are the directions of the positronium decay photons. To a sensitivity of 2.2 × 10 −3 , no CP -violation has been found, which is at the level of the CP -violation amplitude in the K meson. A 90% confidence interval of the CP -violation parameter (CCP ) was determined to be −0.0023 < CCP < 0.0049. This result is a factor 7 more strict than that of the previous experiment.The material state of the universe results only because of its matter-antimatter asymmetry. To understand the origin of this asymmetry is one of particle physics' most urgent goals. One cause could be the CPviolation (charge conjugation and parity) in the quark sector, which was found both in the K [1] and B [2] mesons. The CP -violating processes in B mesons have been measured precisely [3] using its various decay processes at KEKB and PEP-II and they can be well described with the Kobayashi-Maskawa theory [4]. While understanding the origin of CP -violation in the quark sector is a great achievement, the resulting asymmetry may be too small to result in the amount of matter in the Universe [5]. All CP -violating observables in the Standard Model are proportional to the Jarlskog invariance, J= s 2 1 s 2 s 3 c 1 c 2 c 3 sin(δ) ∼ 3 × 10 −5 , where c i are s i are the mixing angles in the KM matrix, and δ is the CP -violating phase. The CP -violating observables are also suppressed by the Higgs vacuum expectation value, 1/v 12 , since non-equilibrium can occur in the electroweak phase transition in the Standard Model. It seems that these violations alone are too small to accout for the observed baryons in the universe. A new source of CP -violation or a new mechanism is necessary, and CPviolation in the lepton sector [6] is a good candidate. Leptonic CP -violation has not yet been observed despite many studies at various neutrino factories [7].Positronium (Ps) is a neutral system comprising an electron and a positron and is the analogue of the neutral meson. If CP is violated in the lepton sector, such neutral systems (e.g. Ps, muonium) are good test candidates since the admixture of opposite CP eigenstates will occur. The search for CP -violation in Ps has been performed previously and no CP violation was found at the 1.5% level of uncertainty [9].If CP -symmetry is not conserved in Ps, the decay rate of the triplet Ps (o-Ps) is dependent on the CP -violating term. The number of o-Ps decay events would be expressed as (1) where S is the spin of the o-Ps, k i is the direction of the i-th energetic γ-ray from the decay (| k i |=1), and τ is the lifetime of o-Ps. C CP is the amplitude of the CP -violation. The Standard Model prediction for C CP is of the order of 10 −10 [10]. This is due to photonphoton interactions in the final state. Another exotic decay cont...

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“…Thus the angular correlation is CP -odd and T odd but conserves CP T symmetry. This correlation would appear in general [10] when the CP -violating effect exists in Ps.…”

mentioning

confidence: 90%

“…C CP is the amplitude of the CP -violation. The Standard Model prediction for C CP is of the order of 10 −10 [10]. This is due to photonphoton interactions in the final state.…”

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confidence: 97%

Search forCPViolation in Positronium Decay

et al. 2010

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“…An ideal object for this kind of studies is the positronium atom: a system of lepton and antilepton bound via electromagnetic interaction. A test of the discrete symmetries in the decays of positronium into photons is limited by the photon-photon interaction which is expected to mimic the symmetry violation at the level of about 10 −9 only [10,11]. This is still about six orders of magnitude smaller than the present experimental limits equal to about 3×10 −3 [12,13].…”

Section: Introductionmentioning

confidence: 53%

Studies of discrete symmetries in a purely leptonic system using the Jagiellonian Positron Emission Tomograph

et al. 2016

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Abstract. Discrete symmetries such as parity (P), charge-conjugation (C) and time reversal (T) are of fundamental importance in physics and cosmology. Breaking of charge conjugation symmetry (C) and its combination with parity (CP) constitute necessary conditions for the existence of the asymmetry between matter and antimatter in the observed Universe. The presently known sources of discrete symmetries violations can account for only a tiny fraction of the excess of matter over antimatter. So far CP and T symmetries violations were observed only for systems involving quarks and they were never reported for the purely leptonic objects. In this article we describe briefly an experimental proposal for the test of discrete symmetries in the decays of positronium atom which is made exclusively of leptons. The experiments are conducted by means of the Jagiellonian Positron Emission Tomograph (J-PET) which is constructed from strips of plastic scintillators enabling registration of photons from the positronium annihilation. J-PET tomograph together with the positronium target system enable to measure expectation values for the discrete symmetries odd operators constructed from (i) spin vector of the ortho-positronium atom, (ii) momentum vectors of photons originating from the decay of positronium, and (iii) linear polarization direction of annihilation photons. Linearly polarized positronium will be produced in the highly porous aerogel or polymer targets, exploiting longitudinally polarized positrons emitted by the sodium 22 Na isotope. Information about the polarization vector of orthopositronium will be available on the event by event basis and will be reconstructed from the known position of the positron source and the reconstructed position of the orthopositronium annihilation. In 2016 the first tests and calibration runs are planned, and the data collection with high statistics will commence in the year 2017.

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“…CP violation in the o-Ps decay can be detected by an accurate measurement of the angular correlation between the o-Ps spinS O P and the momenta of the photons from the o-Ps decay [915], as shown in Eq. (7.1).…”

Section: Measurement Of Cp Violation In Ortho-positronium Decaymentioning

confidence: 99%

Flavor physics of leptons and dipole moments

Raidal¹,

Schaaf²,

Bigi³

et al. 2009

Flavor in the Era of the LHC

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This chapter of the report of the "Flavour in the era of the LHC" Workshop discusses the theoretical, phenomenological and experimental issues related to flavour phenomena in the charged lepton sector and in flavour-conserving CP-violating processes. We review the current experimental limits and the main theoretical models for the flavour structure of fundamental particles. We analyze the phenomenological consequences of the available data, setting constraints on explicit models beyond the Standard Model, presenting benchmarks for the discovery potential of forthcoming measurements both at the LHC and at low energy, and exploring options for possible future experiments.

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How to testCP, T, andCPT invariance in the three photon decay of polarized3 S 1 positronium

Cited by 64 publications

References 19 publications

Search forCPViolation in Positronium Decay

Search forCPViolation in Positronium Decay

Studies of discrete symmetries in a purely leptonic system using the Jagiellonian Positron Emission Tomograph

Flavor physics of leptons and dipole moments

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