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'{{short description|hypothetical counterpart to ordinary matter}} {{update|date=June 2019}} {{Distinguish|antimatter|mirror universe}} 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 particle]]s respect rotation and translation symmetry but do not respect [[P-symmetry|mirror reflection symmetry]] (also called P-symmetry or parity). Of the [[Four fundamental forces|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">{{Cite journal |doi=10.1103/PhysRev.104.254 |title=Question of Parity Conservation in Weak Interactions |journal=Physical Review |volume=104 |issue = 1 |pages=254–258 |year=1956 |last1=Lee |first1=T. D. |last2=Yang |first2=C. N. |bibcode = 1956PhRv..104..254L}} {{Errata |bibcode=1957PhRv..106.1371L |doi=10.1103/PhysRev.106.1371 |checked=yes}}</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">{{Cite journal | doi=10.1103/PhysRev.105.1413|title = Experimental Test of Parity Conservation in Beta Decay| journal=Physical Review| volume=105| issue=4| pages=1413–1415|year = 1957|last1 = Wu|first1 = C. S.| last2=Ambler| first2=E.| last3=Hayward| first3=R. W.| last4=Hoppes| first4=D. D.| last5=Hudson| first5=R. P.| bibcode=1957PhRv..105.1413W| doi-access=free}}</ref><ref>{{Cite journal | doi=10.1103/PhysRev.105.1415|title = Observations of the Failure of Conservation of Parity and Charge Conjugation in Meson Decays: The Magnetic Moment of the Free Muon| journal=Physical Review| volume=105| issue=4| pages=1415–1417|year = 1957|last1 = Garwin|first1 = Richard L.| last2=Lederman| first2=Leon M.| last3=Weinrich| first3=Marcel| bibcode=1957PhRv..105.1415G| doi-access=free}}</ref><ref>{{Cite journal | doi=10.1103/PhysRev.106.1290|title = Nuclear Emulsion Evidence for Parity Nonconservation in the Decay Chain π⁺→μ⁺→e⁺| journal=Physical Review| volume=106| issue=6| pages=1290–1293|year = 1957|last1 = Friedman|first1 = Jerome I.| last2=Telegdi| first2=V. L. |bibcode=1957PhRv..106.1290F}}</ref> However, parity symmetry 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">{{Cite journal |doi = 10.1016/0370-2693(91)91013-L|title = A model with fundamental improper spacetime symmetries|journal = Physics Letters B|volume = 272|issue = 1–2|pages = 67–70|year = 1991|last1 = Foot|first1 = R.|last2 = Lew|first2 = H.|last3 = Volkas|first3 = R.R.|bibcode = 1991PhLB..272...67F}}</ref> although the basic idea dates back further.<ref name="lee"/><ref name="kob">{{cite journal |first=I. |last=Kobzarev |first2=L. |last2=Okun |first3=I. |last3=Pomeranchuk |title=On the possibility of observing mirror particles |journal=Soviet Journal of Nuclear Physics |volume=3 |page=837 |year=1966}}</ref><ref name="pav">{{Cite journal |arxiv = hep-ph/0105344 |doi = 10.1007/BF01810695 |title = External inversion, internal inversion, and reflection invariance |journal = International Journal of Theoretical Physics |volume = 9 |issue = 4 |pages = 229–244 |year = 1974 |last1 = Pavšič |first1 = Matej |bibcode = 1974IJTP....9..229P}}</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">{{Cite journal |arxiv = hep-ph/9505385 |doi = 10.1103/PhysRevD.52.6607 |pmid = 10019200 |title = Reconciling present neutrino puzzles: Sterile neutrinos as mirror neutrinos |journal = Physical Review D |volume = 52 |issue = 11 |pages = 6607–6611 |year = 1995 |last1 = Berezhiani |first1 = Zurab G. |last2 = Mohapatra |first2 = Rabindra N. |bibcode = 1995PhRvD..52.6607B}}</ref><ref name="flv">{{Cite journal |arxiv = hep-ph/0006027 |doi = 10.1088/1126-6708/2000/07/032 |title = Unbroken versus broken mirror world: A tale of two vacua |journal = Journal of High Energy Physics |volume = 2000 |issue = 7 |pages = 032 |year = 2000 |last1 = Foot |first1 = Robert |last2 = Lew |first2 = Henry |last3 = Volkas |first3 = Raymond Robert |bibcode = 2000JHEP...07..032F}}</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 use the weak force to interact 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>{{Cite web | url=https://www.bbc.co.uk/dna/h2g2/A1164052 | title=H2g2 - Mirror Matter: The Invisible Universe}}</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 | last = Blinnikov |first=S. I. |last2=Khlopov |first2=M. Yu. | year = 1982 | title = On possible effects of 'mirror' particles | url = | journal = Soviet Journal of Nuclear Physics | volume = 36 | issue = | page = 472 }}</ref><ref name="blin2">{{cite journal | last = Blinnikov |first=S. I. |last2=Khlopov |first2=M. Yu. | 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 = 6010 | pages = 415–419 | doi = 10.1038/314415a0 | bibcode = 1985Natur.314..415K }}</ref><ref name="khlp">{{cite journal |first=M. Yu. |last=Khlopov |first2=G. M. |last2=Beskin |first3=N. E. |last3=Bochkarev |first4=L. A. |last4=Pushtilnik |first5=S. A. |last5=Pushtilnik |title=Observational physics of mirror world |journal=Astron. Zh. Akad. Nauk SSSR |volume=68 |pages=42–57 |year=1991 |url=http://lss.fnal.gov/archive/1989/pub/Pub-89-193-A.pdf |archive-url=https://web.archive.org/web/20110605225123/http://lss.fnal.gov/archive/1989/pub/Pub-89-193-A.pdf |archive-date=2011-06-05 |url-status=live}}</ref><ref name="hodg">{{cite journal | author = Hodges H. M. | year = 1993 | title = Mirror baryons as the dark matter | journal = Physical Review D| volume = 47 | issue = 2 | pages = 456–459 | bibcode = 1993PhRvD..47..456H | doi = 10.1103/PhysRevD.47.456 | pmid = 10015599 }}</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 = Modern Physics Letters A| volume = 16 | issue = 2 | pages = 53–62 | doi = 10.1142/S0217732301002274 | bibcode = 2001MPLA...16...53T | arxiv = hep-ph/0010147 }}</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 = Physics Letters B| volume = 489 | issue = 3–4 | pages = 420–426 | doi = 10.1016/S0370-2693(00)00942-4 | citeseerx = 10.1.1.347.9373 | bibcode = 2000PhLB..489..420T | arxiv = hep-ph/0006262 }}</ref> aalia ==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">{{Cite journal |doi = 10.1016/0370-2693(86)90540-X|title = Positronium versus the mirror universe|journal = Physics Letters B|volume = 167|issue = 1|pages = 35–36|year = 1986|last1 = Glashow|first1 = S.L.|bibcode = 1986PhLB..167...35G}}</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">{{Cite journal |arxiv = hep-ex/0311031|doi = 10.1142/S0217751X04020105|title = An Apparatus to Search for Mirror Dark Matter|journal = International Journal of Modern Physics A|volume = 19|issue = 23|pages = 3833–3847|year = 2004|last1 = Gninenko|first1 = S. N.|bibcode = 2004IJMPA..19.3833G}}</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">{{Cite journal |arxiv = hep-ph/0308254|doi = 10.1103/PhysRevD.69.036001|title = Implications of the DAMA and CRESST experiments for mirror matter-type dark matter|journal = Physical Review D|volume = 69|issue = 3|pages = 036001|year = 2004|last1 = Foot|first1 = R.|bibcode = 2004PhRvD..69c6001F}}</ref><ref name="foot4">{{Cite journal |arxiv = astro-ph/0405362|doi = 10.1142/S0217732304015051|title = Reconciling the Positive Dama Annual Modulation Signal with the Negative Results of the CDSM II Experiment|journal = Modern Physics Letters A|volume = 19|issue = 24|pages = 1841–1846|year = 2004|last1 = Foot|first1 = R.|bibcode = 2004MPLA...19.1841F}}</ref> ===Electromagnetic effects=== Mirror matter may also be detected in electromagnetic field penetration experiments<ref name="mitra">{{Cite journal |arxiv = astro-ph/0605369|doi = 10.1103/PhysRevD.74.043532|title = Detecting dark matter in electromagnetic field penetration experiments|journal = Physical Review D|volume = 74|issue = 4|pages = 043532|year = 2006|last1 = Mitra|first1 = Saibal|bibcode = 2006PhRvD..74d3532M}}</ref> and there would also be consequences for planetary science<ref name="footm">{{Cite journal |arxiv = astro-ph/0211067|doi = 10.1016/S0927-6505(03)00119-1|title = Mirror matter in the solar system: New evidence for mirror matter from Eros|journal = Astroparticle Physics|volume = 19|issue = 6|pages = 739–753|year = 2003|last1 = Foot|first1 = R.|last2 = Mitra|first2 = S.|bibcode = 2003APh....19..739F}}</ref><ref name="footsil">{{Cite journal |arxiv = astro-ph/0104251|last1 = Pavsic|first1 = Matej|last2 = Silagadze|first2 = Z. K.|title = Do mirror planets exist in our solar system?|journal = Acta Physica Polonica B|volume = 32|issue = 7|pages = 2271|year = 2001|bibcode = 2001AcPPB..32.2271F}}</ref> and astrophysics.<ref name="adarp">{{Cite journal |arxiv = astro-ph/0205059|doi = 10.1142/S021773230200926X|title = Improved Limits on Photon Velocity Oscillations|journal = Modern Physics Letters A|volume = 17|issue = 38|pages = 2491–2496|year = 2002|last1 = De Angelis|first1 = Alessandro|last2 = Pain|first2 = Reynald|bibcode = 2002MPLA...17.2491D}}</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">{{Cite journal |arxiv = hep-ph/9908257|doi = 10.1103/PhysRevD.62.083512|title = Ultrahigh energy neutrinos from hidden-sector topological defects|journal = Physical Review D|volume = 62|issue = 8|pages = 083512|year = 2000|last1 = Berezinsky|first1 = V.|last2 = Vilenkin|first2 = A.|bibcode = 2000PhRvD..62h3512B}}</ref> Another possible way to evade the GZK bound is via neutron–mirror neutron oscillations.<ref name="uhecrn1">{{Cite journal |arxiv = hep-ph/0507031|doi = 10.1103/PhysRevLett.96.081801|pmid = 16606167|title = Neutron–Mirror-Neutron Oscillations: How Fast Might They Be?|journal = Physical Review Letters|volume = 96|issue = 8|pages = 081801|year = 2006|last1 = Berezhiani|first1 = Zurab|last2 = Bento|first2 = Luís|bibcode = 2006PhRvL..96h1801B}}</ref><ref name="uhecrn2">{{Cite journal |arxiv = hep-ph/0602227|doi = 10.1016/j.physletb.2006.03.008|title = Fast neutron–mirror neutron oscillation and ultra high energy cosmic rays|journal = Physics Letters B|volume = 635|issue = 5–6|pages = 253–259|year = 2006|last1 = Berezhiani|first1 = Zurab|last2 = Bento|first2 = Luís|bibcode = 2006PhLB..635..253B}}</ref><ref name="uhecrn3">{{Cite journal |arxiv = hep-ph/0508109|doi = 10.1016/j.physletb.2005.08.101|title = Some implications of neutron mirror neutron oscillation|journal = Physics Letters B|volume = 627|issue = 1–4|pages = 124–130|year = 2005|last1 = Mohapatra|first1 = R.N.|last2 = Nasri|first2 = S.|last3 = Nussinov|first3 = S.}}</ref><ref name="uhecrn4">{{Cite journal |arxiv = nucl-ex/0601017|doi = 10.1016/j.physletb.2006.06.005|title = On the experimental search for neutron → mirror neutron oscillations|journal = Physics Letters B|volume = 639|issue = 3–4|pages = 214–217|year = 2006|last1 = Pokotilovski|first1 = Yu.N.|bibcode = 2006PhLB..639..214P}}</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">{{Cite journal |bibcode = 1999PhLB..462..302M|title = Mirror matter MACHOs|journal = Physics Letters B|volume = 462|issue = 3–4|pages = 302–309|last1 = Mohapatra|first1 = R. N.|last2 = Teplitz|first2 = Vigdor L.|year = 1999|arxiv = astro-ph/9902085|doi = 10.1016/S0370-2693(99)00789-3}}</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">{{Cite journal |arxiv = astro-ph/9902065|doi = 10.1016/S0370-2693(99)00230-0|title = Have mirror stars been observed?|journal = Physics Letters B|volume = 452|issue = 1–2|pages = 83–86|year = 1999|last1 = Foot|first1 = R.|bibcode = 1999PhLB..452...83F}}</ref> ==See also== {{col div|colwidth=30em}} * {{annotated link|Antimatter}} * {{annotated link|Dark energy}} * {{annotated link|Dark matter}} * {{annotated link|Gravitational interaction of antimatter}} * {{annotated link|Negative energy}} * {{annotated link|Negative mass}} * {{annotated link|Strange matter}} * {{annotated link|QCD matter}} {{colend}} ==References== {{reflist}} ==External links== * [http://people.zeelandnet.nl/smitra/mirror.htm A collection of scientific articles on various aspects of mirror matter theory] * [https://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 | issue=10 | journal=International Journal of Modern Physics D | pages=2161–2192| bibcode=2004IJMPD..13.2161F | year=2004 }} * {{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 | issue=4 |journal=Physics-Uspekhi |pages=380–389|bibcode=2007PhyU...50..380O | year=2007 }} * {{cite journal|author=Z.K. Silagadze | arxiv=hep-ph/0002255 |title=TeV scale gravity, mirror universe, and ... dinosaurs| journal= Acta Physica Polonica B| volume=32 | issue=1 | pages=99–128 | year=2001 | bibcode=2001AcPPB..32...99S }} {{Dark matter}} {{DEFAULTSORT:Mirror Matter}} [[Category:Particle physics]] [[Category:Astroparticle physics]] [[Category:Dark matter]] [[Category:Hypothetical particles]]'