Editing BaBar experiment (section)

== Physics ==
BaBar was set up to understand the [[baryon asymmetry|disparity]] between the [[matter]] and [[antimatter]] content of the universe by measuring [[CP violation|Charge Parity violation]]. [[CP symmetry]] is a combination of [[C symmetry|'''C'''harge-conjugation]] symmetry (C symmetry) and [[P symmetry|'''P'''arity]] symmetry (P symmetry), each of which are conserved separately except in [[weak interaction]]s. BaBar focuses on the study of CP violation in the [[B meson]] system. The name of the experiment is derived from the nomenclature for the B meson (symbol '''{{SubatomicParticle|B}}''') and its [[antiparticle]] (symbol '''{{SubatomicParticle|AntiB}}''', pronounced '''B bar'''). The experiment's [[mascot]] was accordingly chosen to be [[Babar the Elephant]].

If CP symmetry holds, the [[decay rate]] of B mesons and their [[antiparticle]]s should be equal. Analysis of secondary particles produced in the BaBar detector showed this was not the case – in the summer of 2002, definitive results were published based on the analysis of 87 million {{SubatomicParticle|B}}/{{SubatomicParticle|AntiB}} meson-pair events, clearly showing the decay rates were not equal. Consistent results were found by the [[Belle experiment]] at the [[KEK laboratory]] in Japan.

CP violation was already predicted by the [[Standard Model]] of [[particle physics]], and well established in the [[Kaon#CP violation in neutral meson oscillations|neutral kaon system]] ({{SubatomicParticle|link=yes|Kaon}}/{{SubatomicParticle|link=yes|Antikaon}} meson pairs). The BaBar experiment has increased the accuracy to which this effect has been experimentally measured. Currently, results are consistent with the [[Standard Model]], but further investigation of a greater variety of decay modes may reveal discrepancies in the future.

The BaBar detector is a multilayer [[particle detector]]. Its large [[solid angle]] coverage (near [[Hermetic detector|hermetic]]), vertex location with precision on the order of 10&nbsp;[[micrometre|μm]] (provided by a silicon vertex detector), good [[pion]]–[[kaon]] separation at multi-[[GeV]] momenta (provided by a novel [[Cherenkov effect|Cherenkov]] detector), and few-percent precision electromagnetic calorimetry (CsI(Tl) scintillating crystals) allow a list of other scientific searches apart from CP violation in the B meson system.<ref>{{Cite journal | last1 = Aubert | first1 = B. | last2 = Bazan | first2 = A. | last3 = Boucham | first3 = A. | last4 = Boutigny | first4 = D. | last5 = De Bonis | first5 = I. | last6 = Favier | first6 = J. | last7 = Gaillard | first7 = J. -M. | last8 = Jeremie | first8 = A. | last9 = Karyotakis | first9 = Y. | last10 = Le Flour | first10 = T. | last11 = Lees | first11 = J. P. | last12 = Lieunard | first12 = S. | last13 = Petitpas | first13 = P. | last14 = Robbe | first14 = P. | last15 = Tisserand | first15 = V. | last16 = Zachariadou | first16 = K. | last17 = Palano | first17 = A. | last18 = Chen | first18 = G. P. | last19 = Chen | first19 = J. C. | last20 = Qi | first20 = N. D. | last21 = Rong | first21 = G. | last22 = Wang | first22 = P. | last23 = Zhu | first23 = Y. S. | last24 = Eigen | first24 = G. | last25 = Reinertsen | first25 = P. L. | last26 = Stugu | first26 = B. | last27 = Abbott | first27 = B. | last28 = Abrams | first28 = G. S. | last29 = Amerman | first29 = L. | last30 = Borgland | first30 = A. W. | title = The BABAR detector | doi = 10.1016/S0168-9002(01)02012-5 | journal = Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | volume = 479 | issue = 1 | pages = 1–116 | year = 2002 |arxiv = hep-ex/0105044 |bibcode = 2002NIMPA.479....1A | s2cid = 117579419 | display-authors = 29 }}</ref> Studies of rare decays and searches for exotic particles and precision measurements of phenomena associated with mesons containing [[bottom quark|bottom]] and [[charm quark]]s, as well as phenomena associated with [[tau lepton]]s are possible.

The BaBar detector ceased operation on 7 April 2008, but data analysis is ongoing.