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'{{Distinguish|antimatter}} In [[physics]], '''mirror matter''', also called '''shadow matter''' or '''Alice matter''', is a hypothetical counterpart to ordinary matter. ==Overview== Modern physics deals with three basic types of spatial [[symmetry]]: [[Reflection (mathematics)|reflection]], [[Rotation (mathematics)|rotation]], and [[Translation (physics)|translation]]. The known elementary particles respect rotation and translation symmetry but do not respect [[P-symmetry|mirror reflection symmetry]] (also called P-symmetry or parity). Of the four fundamental interactions—[[electromagnetism]], the [[strong interaction]], the [[weak interaction]], and [[gravitation|gravity]]—only the weak interaction breaks parity. Parity violation in weak interactions was first postulated by [[Tsung Dao Lee]] and [[Chen Ning Yang]]<ref name="lee">T. D. Lee and C. N. Yang, ''Question of Parity Conservation in Weak Interactions'', Phys. Rev. '''104''', 254&ndash;258 (1956) [http://link.aps.org/abstract/PR/v104/p254 article], Erratum ibid '''106''', 1371 (1957) [http://link.aps.org/abstract/PR/v106/p1371 Erratum]</ref> in 1956 as a solution to the [[Kaon#Parity violation|τ-θ puzzle]]. They suggested a number of experiments to test if the weak interaction is invariant under parity. These experiments were performed half a year later and they confirmed that the weak interactions of the known particles violate parity.<ref name="wu">C. S. Wu, E. Ambler, R. W. Hayward, D. D. Hopes and R. R. Hudson, ''Experimental test of parity conservation in beta decay'', Phys. Rev. '''105''', 1413 (1957).</ref><ref>R. L. Garwin, L.M. Lederman and M. Weinrich, ''Observations of the failure of conservation of parity and charge conjugation in meson decays: The magnetic moment of the free muon'', Phys. Rev. '''105''', 1415 (1957).</ref><ref>J. J. Friedman and V. L. Telegdi, ''Nuclear emulsion evidence for parity nonconservation in the decay chain <math>\pi^{+}\rightarrow\mu^{+}\rightarrow e^{+}</math>'', Phys. Rev. '''105''', 1681 (1957).</ref> However, parity symmetry fart fuck me in the pussy can be restored as a fundamental symmetry of nature if the particle content is enlarged so that every particle has a mirror partner. The theory in its modern form was described in 1991,<ref name="foot">R. Foot, H. Lew and R. R. Volkas, ''A model with fundamental improper space-time symmetries'', Physics Letters B272, 67 (1991)</ref> although the basic idea dates back further.<ref name="lee"/><ref name="kob">I. Kobzarev, L. Okun and I. Pomeranchuk, ''On the possibility of observing mirror particles'', Sov. J. Nucl. Phys. '''3''', 837 (1966).</ref><ref name="pav">M. Pavsic, ''External Inversion, Internal Inversion, and Reflection Invariance'', Int. J. Theor. Phys. '''9''', 229-244 (1974) [http://arxiv.org/abs/hep-ph/0105344 preprint].</ref> Mirror particles interact amongst themselves in the same way as ordinary particles, except where ordinary particles have left-handed interactions, mirror particles have right-handed interactions. In this way, it turns out that mirror reflection symmetry can exist as an exact symmetry of nature, provided that a "mirror" particle exists for every ordinary particle. Parity can also be spontaneously broken depending on the [[Higgs potential]].<ref name="ber">Z. Berezhiani and R. N. Mohapatra, ''Reconciling Present Neutrino Puzzles: Sterile Neutrinos as Mirror Neutrinos'', Phys. Rev. D '''52''', 6607-6611 (1995) [http://arxiv.org/abs/hep-ph/9505385 preprint].</ref><ref name="flv">R. Foot, H. Lew and R. R. Volkas, ''Unbroken versus broken mirror world: a tale of two vacua'', JHEP '''0007''', 032 (2000) [http://arxiv.org/abs/hep-ph/0006027 preprint].</ref> While in the case of unbroken parity symmetry the masses of particles are the same as their mirror partners, in case of broken parity symmetry the mirror partners are lighter or heavier. Mirror matter, if it exists, would need to interact weakly{{clarify|date=September 2016}} with ordinary matter. This is because the forces between mirror particles are mediated by mirror [[boson]]s. With the exception of the [[graviton]], none of the known bosons can be identical to their mirror partners. The only way mirror matter can interact with ordinary matter via forces other than gravity is via [[kinetic mixing]] of mirror bosons with ordinary bosons or via the exchange of [[Holdom particle]]s.<ref>http://www.bbc.co.uk/dna/h2g2/A1164052</ref> These interactions can only be very weak. Mirror particles have therefore been suggested as candidates for the inferred [[dark matter]] in the universe.<ref name="blin1">{{cite journal | author = Blinnikov S. I. | year = 1982 | title = On possible effects of 'mirror' particles | url = | journal = Sov. J. Nucl. Phys. | volume = 36 | issue = | page = 472 }}</ref><ref name="blin2">{{cite journal | author = Blinnikov S. I. | year = 1983 | title = Possible astronomical effects of mirror particles | url = | journal = Sov. Astron | volume = 27 | issue = | pages = 371–375 | bibcode = 1983SvA....27..371B }}</ref><ref name="kolb">{{cite journal | author = Kolb E. W., Seckel M., Turner M. S. | year = 1985 | title = The shadow world of superstring theories | url = | journal = Nature | volume = 314 | issue = | pages = 415–419 | doi = 10.1038/314415a0 | bibcode = 1985Natur.314..415K }}</ref><ref name="khlp">M. Yu. Khlopov, G. M. Beskin, N. E. Bochkarev, L. A. Pushtilnik and S. A. Pushtilnik, ''observational physics of mirror world'', ''Astron. Zh. Akad. Nauk SSSR'' '''68''', 42-57 (1991) [http://lss.fnal.gov/archive/test-preprint/fermilab-pub-89-193-a.shtml preprint] {{webarchive|url=https://web.archive.org/web/20071213124927/http://lss.fnal.gov/archive/test-preprint/fermilab-pub-89-193-a.shtml |date=2007-12-13 }}.</ref><ref name="hodg">{{cite journal | author = Hodges H. M. | year = 1993 | title = Mirror baryons as the dark matter | url = http://link.aps.org/abstract/PRD/v47/p456 | journal = Phys. Rev. D | volume = 47 | issue = | pages = 456–459 | bibcode = 1993PhRvD..47..456H | doi = 10.1103/PhysRevD.47.456 }}</ref> In another context{{which|date=September 2016}}, mirror matter has been proposed to give rise to an effective [[Higgs mechanism]] responsible for the [[electroweak symmetry breaking]]. In such a scenario, mirror [[fermion]]s have masses on the order of 1 TeV since they interact with an additional interaction, while some of the mirror [[boson]]s are identical to the ordinary gauge [[bosons]]. In order to emphasize the distinction of this model from the ones above{{which|date=January 2016}}, these mirror particles are usually called [[katoptron]]s.<ref name=katoptrons>{{cite journal | author = Triantaphyllou G | year = 2001 | title = Mass generation and the dynamical role of the Katoptron group | url = | journal = Mod.Phys.Lett. | volume = A16 | issue = | pages = 53–62 }}</ref><ref name=katoptrons2>{{cite journal | author = Triantaphyllou G., Zoupanos'' G. | year = 2000 | title = Strongly interacting fermions from a higher dimensional unified gauge theory | url = | journal = Phys.Lett. | volume = B489 | issue = | pages = 420–426 }}</ref> ==Observational effects== ===Abundance=== Mirror matter could have been diluted to unobservably low densities during the [[Cosmic inflation|inflation]] epoch. [[Sheldon Lee Glashow|Sheldon Glashow]] has shown that if at some high energy scale particles exist which interact strongly with both ordinary and mirror particles, [[Effective field theory|radiative corrections]] will lead to a mixing between [[photon]]s and [[mirror photon]]s.<ref name="glas">S. L. Glashow, ''Positronium versus the mirror universe'', Phys. Lett. B '''167''', 35-36 (1986) [https://dx.doi.org/10.1016/0370-2693(86)90540-X article].</ref> This mixing has the effect of giving mirror electric charges a very small ordinary electric charge. Another effect of photon–mirror photon mixing is that it induces oscillations between [[positronium]] and mirror positronium. Positronium could then turn into mirror positronium and then decay into mirror photons. The mixing between photons and mirror photons could be present in tree level [[Feynman diagram]]s or arise as a consequence of quantum corrections due to the presence of particles that carry both ordinary and mirror charges. In the latter case, the quantum corrections have to vanish at the one and two loop level Feynman diagrams, otherwise the predicted value of the kinetic mixing parameter would be larger than experimentally allowed.<ref name="glas"/> An experiment to measure this effect is currently being planned.<ref name="bad">A. Badertscher ''et al.'', ''An apparatus to search for mirror dark matter via the invisible decay of orthopositronium in vacuum'', Int. J. Mod. Phys. A '''19''', 3833-3848 (2004) [http://arxiv.org/abs/hep-ex/0311031 preprint].</ref> ===Dark matter=== If mirror matter does exist in large abundances in the universe and if it interacts with ordinary matter via photon-mirror photon mixing, then this could be detected in dark matter direct detection experiments such as [[DAMA/NaI]] and its successor [[DAMA/LIBRA]]. In fact, it is one of the few dark matter candidates which can explain the positive DAMA/NaI dark matter signal whilst still being consistent with the null results of other dark matter experiments.<ref name="foot3">R. Foot, ''Implications of the DAMA and CRESST experiments for mirror matter-type dark matter'', Phys. Rev. D '''69''', 036001 (2004) [http://arxiv.org/abs/hep-ph/0308254 preprint].</ref><ref name="foot4">R. Foot, ''Reconciling the positive DAMA annual modulation signal with the negative results of the CDMS II experiment'', Mod. Phys. Lett. A '''19''', 1841-1846 (2004) [http://arxiv.org/abs/astro-ph/0405362 preprint].</ref> ===Electromagnetic effects=== Mirror matter may also be detected in electromagnetic field penetration experiments<ref name="mitra">S. Mitra, ''Detecting dark matter in electromagnetic field penetration experiments'', Phys. Rev. D '''74''', 043532 (2006) [http://arxiv.org/abs/astro-ph/0605369 preprint].</ref> and there would also be consequences for planetary science<ref name="footm">R. Foot and S. Mitra, ''Mirror matter in the solar system: New evidence for mirror matter from Eros'', Astropart. Phys. '''19''', 739-753 (2003) [http://arxiv.org/abs/astro-ph/0211067 preprint].</ref><ref name="footsil">R. Foot and Z.K. Silagadze, ''Do mirror planets exist in our solar system?'' Acta Phys. Polon. B '''32''', 2271-2278 (2001) [https://arxiv.org/abs/astro-ph/0104251 abstract].</ref> and astrophysics.<ref name="adarp">A. De Angelis and R. Pain, ''Improved limits on photon velocity oscillations'', Mod. Phys. Lett. A '''17''', 2491-2496 (2002) [http://arXiv.org/abs/astro-ph/0205059v1 preprint].</ref> ===GZK puzzle=== Mirror matter could also be responsible for the [[Greisen-Zatsepin-Kuzmin limit#Cosmic ray paradox|GZK puzzle]]. [[Topological defect]]s in the mirror sector could produce mirror neutrinos which can oscillate to ordinary neutrinos.<ref name="uhecrtd">V. Berezinsky and A. Vilenkin, ''Ultra high energy neutrinos from hidden-sector topological defects'', Phys. Rev. D '''62''', 083512 (2000) [http://arxiv.org/abs/hep-ph/9908257 preprint].</ref> Another possible way to evade the GZK bound is via neutron–mirror neutron oscillations.<ref name="uhecrn1">Z. Berezhiani and L. Bento, ''Neutron - Mirror Neutron Oscillations: How Fast Might They Be?'', Phys. Rev. Lett. '''96''', 081801 (2006) [http://arxiv.org/abs/hep-ph/0507031 preprint].</ref><ref name="uhecrn2">Z. Berezhiani and L. Bento, ''Fast Neutron - Mirror Neutron Oscillation and Ultra High Energy Cosmic Rays'', Phys. Lett. B '''635''', 253-259 (2006) [http://arxiv.org/abs/hep-ph/0602227 preprint].</ref><ref name="uhecrn3">R. N. Mohapatra, S. Nasri and S. Nussinov, ''Some Implications of Neutron Mirror Neutron Oscillation'', Phys. Lett. B '''627''', 124-130 (2005) [http://arxiv.org/abs/hep-ph/0508109 preprint].</ref><ref name="uhecrn4">Yu. N. Pokotilovski, ''On the experimental search for neutron -- mirror neutron oscillations'', Phys. Lett. B '''639''', 214-217 (2006) [http://arxiv.org/abs/nucl-ex/0601017 preprint].</ref> ===Gravitational effects=== If mirror matter is present in the universe with sufficient abundance then its gravitational effects can be detected. Because mirror matter is analogous to ordinary matter, it is then to be expected that a fraction of the mirror matter exists in the form of mirror galaxies, mirror stars, mirror planets etc. These objects can be detected using gravitational [[microlensing]].<ref name="mohapatra">R. N. Mohapatra and V. L. Teplitz, ''Mirror matter MACHOs.'' Phys. Lett. B, '''462''', 302 - 309 (1999) [http://adsabs.harvard.edu/abs/1999PhLB..462..302M article].</ref> One would also expect that some fraction of stars have mirror objects as their companion. In such cases one should be able to detect periodic [[Doppler shift]]s in the spectrum of the star.<ref name="khlp"/>{{dead link|date=March 2017}} There are some hints that such effects may already have been observed.<ref name="foot1">R. Foot, ''Have mirror stars been observed?'', Phys. Lett. B '''452''', 83-86 (1999) [http://arxiv.org/abs/astro-ph/9902065 preprint].</ref><ref name="foot2">R. Foot, ''Have mirror planets been observed?'', Phys. Lett. B '''471''', 191-194 (1999) [http://arxiv.org/abs/astro-ph/9908276 preprint].</ref> ==See also== * [[Antimatter]] * [[Dark energy]] * [[Dark matter]] * [[Gravitational interaction of antimatter]] * [[Negative energy]] * [[Negative mass]] * [[Strange matter]] * [[QCD matter]] ==References== {{reflist}} ==External links== * [http://people.zeelandnet.nl/smitra/mirror.htm A collection of scientific articles on various aspects of mirror matter theory] * [http://www.bbc.co.uk/dna/h2g2/A1300429 Mirror matter] article on [[h2g2]] * {{cite journal|author=R. Foot | arxiv=astro-ph/0407623 | title = Mirror matter type dark matter | doi=10.1142/S0218271804006449 | volume=13 | journal=International Journal of Modern Physics D | pages=2161–2192| bibcode=2004IJMPD..13.2161F }} * {{cite journal|author=L.B. Okun | arxiv=hep-ph/0606202 |title=Mirror particles and mirror matter: 50 years of speculation and search | doi=10.1070/PU2007v050n04ABEH006227 |volume=50 |journal=Physics-Uspekhi |pages=380–389|bibcode=2007PhyU...50..380O }} * {{cite arxiv|author=Z.K. Silagadze | eprint=hep-ph/0002255 |title=TeV scale gravity, mirror universe, and ... dinosaurs}} {{Dark matter}} {{DEFAULTSORT:Mirror Matter}} [[Category:Particle physics]] [[Category:Astroparticle physics]] [[Category:Dark matter]] [[Category:Hypothetical particles]]'