CP Violation  

In General > s.a. atomic physics; early-universe cosmology; matter [antimatter]; neutrino mixing; particle statistics.
* Idea: One of several possible explanations for the matter-antimatter asymmetry (baryon asymmetry) observed in the universe.
* Theory: Both strong and weak interactions can violate CP (charge-parity) symmetry; The effect can be described in terms of mixing in the CKM matrix (three angles α, β and γ which form a non-degenerate CKM unitarity triangle–the amount of violation is proportional to the area), but could also be due to other physics; The standard model "predicts" a value of sin(2β) between 0.66 and 0.84; Violations are likely to be connected to baryon asymmetry, and maybe neutrino oscillations.
* CKM matrix and unitarity: The entries Vij of the CKM matrix, where i = u, c, t, and j = d, s, b, are the amplitudes for the corresponding flavor-changing processes, and must be unitary; The "unitarity triangle" is the expression one obtains when one writes explicitly one of the unitarity conditions, Vub Vud* + Vcb Vcd* + Vtb Vtd* = 0 (so this vanishing of the sum of three complex numbers is one of six such triangles one can get from Vij, but it is the one that contains the two most significant phases).
* Idea, experiment: Can't measure all three CKM angles in the same experiment (BaBar and Belle measure α and β – although α will require much more data –, but need Bss to measure γ; Weak effects are esier to compare with theory.
* In 2+1 dimensions: P and T are violated by particles with fractional statistics.
> Online resources: see Wikipedia page.

History, Status
* 1957: L Landau argues that, although P can be violated, CP should not be; A Pais & M Gell-Mann suggest that the K0 and K0-bar mesons are linear combinations of parity eigenstates K1 (–1, long-lived, decays into 3π) and K2 (+1, short-lived, decays into 2π); K1 found by L Lederman et al.
1964: Unexpected, first indirect evidence found by Fitch & Cronin (CCFT) in K1 meson decay into 2π [@ news pn(99)mar].
* 1998: Indications found by CDF in B meson decay.
* 1999: Direct evidence in K meson decay at Fermilab, ε'/ε = (28 ± 4) × 10–4, and CERN, (18.5 ± 7) × 10–4.
* 2000: RHIC now online, will search for violations due to strong interaction, as opposed to weak interactions; Results from B meson decay give sin(2β) = 0.45 ± 0.44 ± 0.45 (KEK) and 0.45 ± 0.44 ± 0.45 (BaBar at SLAC).
* 2001: Measurements from B meson decays give sin(2β) = 0.59 ± 0.14 (BaBar at SLAC) and 0.99 ± 0.14 (Belle at KEK); Aleph and CDF give intermediate values; Strong interaction effects not yet seen.
* 2001: Direct violation – Differences between decays B mesons and their antiparticle equivalents at BaBar.
* 2006: The amount of CP violation observed so far is insufficient to account for matter domination (there may be more in quark, neutrino, or Higgs physics).
* 2012: Unexpectedly large violation seen in charmed meson decay.
* 2017: CP violation seen in heavy baryon decays.

References > s.a. CPT [including T-reversal]; modified QED; parity [violation]; theta sectors.
@ Reviews, news: Adair SA(88)feb; news PT(88)oct; Harrison pw(03)jul; news pw(06)apr; Ibrahim & Nath RMP(08); Kobayashi IJMPA(09); Maskawa IJMPA(09); Frère CRP(12)-a1201 [rev].
@ Books: Jarlskog 89; Wolfenstein ed-90; Castelo Branco et al 99 [r PT(00)aug]; Bigi & Sanda 09; Sozzi 12.
@ General articles: Fitch RMP(81); Cronin RMP(81); Rosner AJP(96)aug [demo]; Rosner & Slezak AJP(01)jan [classical analog]; Sozzi & Mannelli RNC(03) [measurements]; Smit JHEP(04)hp [and standard model effective action]; Gershon pw(07)apr [unitarity triangle]; Ashtekar SHPMP-a1307-conf [new perspective].
@ Lepton sector: Branco & Rebelo NJP(05) [and neutrino mass]; Dita PRD(06)-a1101; Farzan & Smirnov JHEP(07); Pascoli et al PRD(07) [and leptogenesis]; Winter PLB(09) [neutrino propagation]; Branco et al RMP(12) [rev]; Fogli et al PRD(12)-a1205 [neutrino masses, mixings and phases]; > s.a. neutrino mixing.
@ Spontaneous violation: Dorey et al JPA(01) [and supersymmetry]; Frampton IJMPA(02); Balaji et al PLB(04) [dynamical, early universe].
@ B-meson decays: Green & McMahon CP(01); Peruzzi RNC(04); Gronau IJMPA(07).
@ Experiments: Abe et al PRL(98), PRL(98); Alavi-Harati et KTeV PRL(00) [KL π+ π e+ e decay]; Abe et Belle PRL(04) [B0π+ π decay]; Fratina et Belle PRL(07) [B0D+ D decay]; Nir Phy(12) [D and anti-D charmed meson decay]; news CERN(13)apr [strange meson decay]; news ibt(16)jun [shape of the Radium-224 and Barium-144 nuclei]; LHCb nPhys(17)jan + news ns(17)feb [in beauty baryon decay].
@ Gravity: Deser et al PLB(80); Losecco et al PLA(89); Anandan PRL(98)ht/97 [global topology]; Mukhopadhyaya & Sengupta PLB(99)ht/98 [with torsion]; Ahluwalia MPLA(98)hp/99; Kobakhidze a0807 [quantum gravity and discontinuity of CP-conserving limit]; Bargueño & Pérez de Tudela PRD(08) [long-range parity violation]; Hadley EPL(11)-a1107 + news sciblog(11)jul [CP violation as a consequence of frame dragging from galactic rotation].
@ Other theories: Khalil IJMPA(03) [supersymmetric]; Creutz ht/03, PRL(04)hl/03, PRL(04) [strong interactions]; Grzadkowski & Wudka PRL(04)hp [5D QED]; Briere Phy(10) [new physics beyond the standard model as source of CP violation]; Ellis et al JHEP(10)-a1006 [geometric approach].

Related Topics > s.a. Charge Conjugation; electromagnetism [dipole moments]; matter [mirror matter]; realism; uncertainty relations.
@ Strong CP problem: Fort & Gambini ht/97 [in loop formulation]; Dine hp/00-ln; Hsu & Sannino PLB(05); Mitra hp/05-conf [no problem]; Takahashi PTP(09)-a0804 [anthropic solution]; Peccei AIP(10)-a1005 [history, and spontaneously-broken chiral symmetry]; Swain a1005 [and the existence of black holes]; Lattanzi & Mercuri PRD(10)-a1006 [solution via the Peccei-Quinn mechanism]; Acharya et al JHEP(10) [M-theory solution]; Hook PRL(15)-a1411 [anomalous solutions].
@ Other: Home & Majumdar FP(99)qp [and Bohmian insert]; Huggett PhSc(00)jun [P violation]; Bertlmann et al PLA(01)qp [and Bell inequalities]; Caliceti et al PLA(05)mp/04 [with CPT symmetry]; Brauner et al PRL(12)-a1110 [temperature dependence of CP violation effects in the Standard Model].

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