MAGIC is an instrument composed of a pair of telescopes for gamma- ray and
cosmic-ray astrophysics in the TeV range. It is operating for more than a
decade now, and is one of the current best performing instruments in this
field, specifically at low energies, where it achieves the largest sensitivity.
MAGIC pursues a strong program in galactic and extragalactic gamma-ray science.
Its catalog of blazars, radiogalaxies and galaxy clusters observations as well
as supernovae, novae, pulsar wind nebulae, pulsars and binary systems has now
increased to several tens of detected targets. In addition, MAGIC is suited for
cosmic ray searches, being sensitive to the signatures of earth-skimming
tau-neutrinos, cosmic antiprotons, and others. Furthermore, MAGIC has a strong
fundamental physics program, with searches for particle dark matter, Lorentz
Invariance violations, axion-like particles and primordial black hole
evaporation, providing important recent constraints in some relevant cases.
Finally, MAGIC has a follow-up program of Gravitational Waves events. Few
highlights topics will be discussed in this contribution.Comment: Proceedings of the 11th SciNeGHE workshops, 18-21 October 2016, Pisa,
  Italy. To appear in Il Nuovo Cimento 

Doro, Michele

English

arXiv

MAGIC is an instrument composed of a pair of telescopes for gamma- ray and cosmic-ray astrophysics in the TeV range. It is operating for more than a decade now, and is one of the current best performing instruments in this field, specifically at low energies, where it achieves the largest sensitivity. MAGIC pursues a strong program in galactic and extragalactic gamma-ray science. Its catalog of blazars, radiogalaxies and galaxy clusters observations as well as supernovae, novae, pulsar wind nebulae, pulsars and binary systems has now increased to several tens of detected targets. In addition, MAGIC is suited for cosmic ray searches, being sensitive to the signatures of earth-skimming tau-neutrinos, cosmic antiprotons, and others. Furthermore, MAGIC has a strong fundamental physics program, with searches for particle dark matter, Lorentz Invariance violations, axion-like particles and primordial black hole evaporation, providing important recent constraints in some relevant cases. Finally, MAGIC has a follow-up program of Gravitational Waves events. Few highlights topics will be discussed in this contribution

Doro, M.

Archivio istituzionale della ricerca - Università di Padova

Original Citation:Gamma-ray, particle and exotic physics at TeV energies with the MAGIC telescopesEditrice Compositori s.r.l.Publisher:Published version:DOI:Terms of use:Open Access(Article begins on next page)This article is made available under terms and conditions applicable to Open Access Guidelines, as described athttp://www.unipd.it/download/file/fid/55401 (Italian only)Availability:This version is available at: 11577/3253015 since: 2017-12-13T12:04:44Z10.1393/ncc/i2017-17115-5Università degli Studi di PadovaPadua Research Archive - Institutional RepositoryDOI 10.1393/ncc/i2017-17115-5Colloquia: SciNeGHE 2016IL NUOVO CIMENTO 40 C (2017) 115Gamma-ray, particle and exotic physics at TeV energieswith the MAGIC telescopesM. DoroUniversita` e Sezione INFN - Via Marzolo 8, I-35131 Padova, Italyreceived 21 April 2017Summary. — MAGIC is an instrument composed of a pair of telescopes for gamma-ray and cosmic-ray astrophysics in the TeV range. It is operating for more thana decade now, and is one of the current best performing instruments in this ﬁeld,speciﬁcally at low energies, where it achieves the largest sensitivity. MAGIC pursuesa strong program in galactic and extragalactic gamma-ray science. Its catalog ofblazars, radiogalaxies and galaxy clusters observations as well as supernovae, novae,pulsar wind nebulae, pulsars and binary systems has now increased to several tensof detected targets. In addition, MAGIC is suited for cosmic ray searches, beingsensitive to the signatures of earth-skimming tau-neutrinos, cosmic antiprotons, andothers. Furthermore, MAGIC has a strong fundamental physics program, withsearches for particle dark matter, Lorentz Invariance violations, axion-like particlesand primordial black hole evaporation, providing important recent constraints insome relevant cases. Finally, MAGIC has a follow-up program of GravitationalWaves events. Few highlights topics will be discussed in this contribution.IntroductionMAGIC (Major Atmospheric Gamma-ray Imaging Cherenkov) is a telescope com-posed of a couple of 17m diameter reﬂector of the IACTA (Imaging AtmosphericCherenkov Telescope Array) class. The technique is based on the observation of theCherenkov radiation generated in extended particle showers produced in the atmosphereby either cosmic particles of high energy cosmic radiation reaching the Earth. The sam-pling of the Cherenkov radiation guarantees good sensitivity, low energy threshold, goodenergy and angular resolutions, compared to shower-front particle detectors, at the ex-pense of a duty cycle limited to dark or moderate moonlit nights. MAGIC is located atthe Canary Island of La Palma (Spain), in the northern hemisphere, at the Observatoriode Roque de Los Muchachos, which will be soon hosting the new IACTA generationof the CTA project. The energy working range is 50GeV to 50TeV, with a sensitivityof 0.66% of the Crab Nebula ﬂux above 220GeV in 50 h [1] and the instrument is inoperation for a decade now.Creative Commons Attribution 4.0 License (http://creativecommons.org/licenses/by/4.0) 12 M. DOROFig. 1. – Science cases with very high energy gamma rays with MAGIC.The MAGIC science program is wide (see ﬁg. 1), and focused on VHE gamma-rayastrophysics. This encompasses relativistic jets physics, plasma physics, magnetic re-connection, diﬀuse shock accelerations, cosmic ray transport and so on, requiring oftenstrong interdisciplinarity. The science pursues can be done in multiple galactic and ex-tragalactic targets and target classes. This will be discussed in sect. 1. However, withnon standard reconstruction algorithm, MAGIC can be operated as a particle detector,in the sense that it can discriminate cosmic particles: protons, electrons, etc. This isthe topic of sect. 2. Finally, MAGIC has the characteristics to be sensitive to someNew Physics scenarios, including dark matter and Lorentz Invariance violation, but also(if existing) to electromagnetic counterparts of gravitational wave events. These will bediscussed in sects. 3 and 4, respectively.Due to space limitation, this contribution will be a brief overview. More detailedreports on MAGIC physics and the success of IACTA can be found for example in [2,3].1. – MAGIC as a TeV gamma-ray detectorThe presence of VHE (Very High Energy: > 100GeV) gamma rays in astrophysicalenvironment is always connected to parent highly accelerated cosmic ray particle (lep-tons and/or hadrons). Therefore gamma ray astrophysics probes cosmic ray physics.However, to be able to understand the particle and radiation ﬁelds in astrophysical en-vironments, a large astronomical framework of knowledge is required, formed by a widemulti-wavelength and multi-instrument contribution. Classical targets for VHE gamma-ray observations were mentioned in the abstract. It is impossible to summarize the manyresults achieved with observation at VHE in the past decade. Only a selection will bediscussed, in which MAGIC has shown unique capabilities.The low MAGIC energy threshold (50GeV), had allowed to search for the farthestsources in the sky, because of the opaqueness of the Universe to VHE gamma rays lostdue to pair production with the UV-IR background radiation ﬁelds of the ExtragalacticBackground Light (EBL), the second radiation ﬁeld permeating the universe after theGAMMA-RAY, PARTICLE AND EXOTIC PHYSICS AT TeV ENERGIES ETC. 3Cosmic Microwave Background (CMB). MAGIC has recently expanded the TeV universeby doubling the distance of the farthest sources known. Two sources at redshift z ∼ 1were detected [4, 5]: the galaxy PKS 1441+25 at z = 0.939 and the galaxy B0218+35at z = 0.944 of which MAGIC did not observe the direct light, but that gravitationallylensed from an intervening spiral galaxy in between. This was the ﬁrst gravitational-lensed delayed VHE signal ever observed.The importance of multi-wavelengths campaign has become utter, and indeed MAGIChas developed several monitoring campaigns and Time of Opportunity programs basedon external triggers. For example, during the Mrk421 campaign reported in [6], thesource had the coverage of Swift-UVOT, Swift-XRT, NuSTAR, Fermi LAT, MAGIC,and VERITAS. The ﬂare event not only generated an increased ﬂux, but also shiftedthe emission peak toward higher energies. In the Synchroton Self-Compton scenarios,this may hint to a diﬀerent (than baseline) electron population that was swept-up or onesingle electron population that was boosted for some mechanism. The energy-dependentvariability provided an important part of the puzzle of the global picture of the targetdynamics. The ﬂares in Active Galactic Nuclei (AGNs) provide useful insights into theassociated Black Hole (BH) physics. All kinds of AGNs in MAGIC catalog have shownextremely fast variability. In 2014, MAGIC saw an impressive ﬂare of the radio-galaxyIC 310. The ﬂux doubled in 4.8 minutes, from an object located at 78Mpc. It isvery unclear what mechanisms could provide such boost because rise-time constraintsemission size: the emission region must have a size smaller than the 20%of the BHsize. The proposed explanation is that particle acceleration occurs by the electric ﬁeldacross a magnetospheric gap at the base of the radio jet, much alike the pulsar radiationmechanism [7].Galaxy clusters are expected to show a diﬀuse gamma-ray emission due to the inter-action of accelerated CR with the ambient intracluster medium. Perseus (78Mpc far) isa cool-core clusters, the brightest in X-ray and thus an optimal lab to search for gammarays associated to accelerated particle ﬁelds in the core. The explanation for the origin ofradio halos is in fact challenging and TeV gamma-ray are an unique probe. TeV gammarays are expected in hadronic model because radio-emitting electrons are secondaries pro-duced by CR protons interacting with the protons of the ICM, or in re-acceleration modelwhere seed population of CR electrons are re-accelerated by interacting turbulent waves.MAGIC observed for 250 h (selected) in 4 years, providing several (model-dependent)constraints. With MAGIC data, we constrained the fraction of the energy dissipated instructure formation shocks that goes into particle acceleration to be not larger than 37%.We limited the cosmic-ray to thermal-pressure ratios to values between 2 and 20%. Weconstrained the magnetic ﬁelds that produce the observed synchrotron emission fromsecondary electrons to be smaller than 10μG [8].Other recent MAGIC results are available here: https://magic.mpp.mpg.de/backend/results/latest.2. – MAGIC as a TeV particle detectorBesides cosmic gamma rays, atmospheric showers are initiated by cosmic rays. Actu-ally, the number of showers generated by the latter class is more than a factor of thousandlarger than those initiated by gamma rays. The ability of IACTA to discriminate betweengamma and particles, and among particles, stems mostly from the diﬀerent imprint inthe camera produced by diﬀerent primaries. MAGIC is routinely used as a particle de-tector. It can perform all-electron searches [9, 10], but in principle can also discriminate4 M. DOROthe charge of the particle by using the shadow of the Moon [11]. MAGIC also follows uptriggers from High Energy events from the IceCube neutrino detector [12].In the following, we focus on the preliminary results MAGIC achieved on the capabilityto discriminate cosmic tau-neutrinos events in the data, thus opening the possibility ofMAGIC as a neutrino detector. This challenging method is based on the fact thatMAGIC, from its mountain location, has a “window of visibility” of 80 × 5 deg2 inthe direction of the Atlantic Ocean, at zenith angles slightly below 90◦. The Ocean isabout 170 km away. By pointing the telescope in this window, MAGIC could detectatmospheric shower generated by tau-leptons emerging from the ocean’s surface, andsoon-after decaying and generating particle showers. In turn, this very energetic tau-lepton (the accessible energy range is beyond the PeV), must have been produced not toodeep inside the ocean by the conversion of a very energetic cosmic tau-neutrino enteringthe Earth in the same MAGIC observing direction. The technique is discussed in [13](and references therein). Tau-induced showers are discriminated because they are createdmuch closer to the telescope compared to any other possible source of background [14].Although the sensitivity to these signals is in principle rather high for MAGIC, at the levelof even above that of IceCube above the PeV range, the prospects for actual detectionof cosmic tau-neutrinos are still thin, due to very low expected ﬂux. This may not bethe case in the occurrence of a strong ﬂare (of an AGN, or a gamma ray bursts, or froma gravitational wave event) where hadrons are expected to be strongly accelerated, thusproviding also an ample neutrino ﬂux. In this case, if the source passed through the“ocean window”, the neutrino ﬂux can be indirectly observed. This observation mode isstill under development in MAGIC. However, even null observation from a ﬂaring sourcecould provide interesting upper limits on the amount of tau-neutrino produced locally,competitive to other instruments in the ﬁeld.3. – MAGIC as a New Physics detectorThere are many theoretical arguments indicating that there may be new Physicsaround the TeV scale. IACTA could be valuable probes for Lorenz Invariance Violations,by observing the time-of-ﬂight delays of photons at diﬀerence energy, a tiny eﬀect pos-sibly ampliﬁed by the cosmological distances at hand [15]; IACTA can probe Axion-likeParticles (ALPs), that may explain the otherwise awkward observation of TeV photonsfrom targets where we expect photons should be hardly observable, because of absorb-ing medium either located at the source (e.g. dense gas ﬁelds) or in the path to thesource. By converting to ALP, faraway TeV photons could thus travel larger distancesthan expected. IACTA can see gamma-ray ﬂashes from fast evaporating Black Holesgenerated in the early Universe and evaporating in these times; ﬁnally, the passage ofexotic objects like magnetic monopoles or quark nuggets, could also generate Cherenkovlight observable with MAGIC (see recent review [16]).However, large attention is paid to IACTA for their capability as dark matter (DM)detectors. They are indeed valuable DM probes, for the following reasons: a) it is oftenthe case that gamma rays are found in prompt annihilation or decay reaction in DM richenvironment, b) the associated gamma ray spectrum, for many DM scenarios, can peakat the TeV and may present peculiar features that can easily diﬀerentiate it from a purelyastrophysical one, c) DM spectra would be universal, so several diﬀerent targets may beobserved with exactly the same spectra, d) the shape of the spectra and its cutoﬀ at theDM mass provide also clues for identiﬁcation of DM besides detection. DM searches aredone with MAGIC at several targets (see a recent review [17]). The cleanest targets inGAMMA-RAY, PARTICLE AND EXOTIC PHYSICS AT TeV ENERGIES ETC. 5the sky are the dwarf galaxies gravitationally bound to the Milky Way and orbiting itsthe DM halo. These are small galaxies, with almost no stellar activity, where DM musthave accreted in large concentrations (mass-to-light ratios thousands of times that of theSun), as seen by stellar velocity dispersion. MAGIC has a large track in observing theseobjects. The recent large campaign (160 h) on the Segue 1 satellite galaxies provided thestrongest constraints from this class of targets above few hundreds of GeV, and receivedthe attention of the Particle Data Group [18].4. – MAGIC as a GW counterpart detectorGravitational waves (GWs) associated physics has recently gained a strong interestdue to multiple detections of GWs by the Ligo Virgo Collaboration (LVC). Although thetheoretical mapping is far from being complete, it is believed that if the merger eventhappen between at least one compact object (NS-NS or NS-BH mergers), a measurablegamma-ray counterpart may be expected, although its spectral energy distribution isunclear. MAGIC can rapidly reposition (< 20 sec) after receiving a GW alert from LVC.However, its small ﬁeld of view (about 10 square degrees) cannot sample but a smallfraction of the LVC region of interest. Despite so, MAGIC has performed follow-ups ofGW161226 [19] and is reﬁning its strategies toward a better selection of pointings.5. – ConclusionsAlthough not the mainstream science, among the MAGIC science goals is that oftrying to add a piece in the puzzle of cosmic ray ﬂuxes at Earth, hunting elusive tau-neutrinos, ﬁnding signatures of New Physics. The astrophysical results are disparate, andfrom tens of of targets and target classes. Result are now contributing to astrophysics in awide multi-instruments and multi-wavelengths scenarios, placing gamma-ray astrophysicsinto the realm of a true astronomical ﬁeld. MAGIC has contributed in many ways to thissuccess along the past 12 years. Few years ahead will be productive until the times comefor the future generation of instruments in this ﬁeld, with the Cherenkov Telescope Arrayobservatory [20] already in construction close to MAGIC at the island of La Palma.REFERENCES[1] MAGIC Collaborations, Astropart. Phys., 72 (2016) 76.[2] Lorenz E. and Wagner R., Eur. Phys. J. H, 37 (2012) 459.[3] Aharonian F. et al., Rep. Prog. Phys., 71 (2008) 096901.[4] MAGIC and Fermi LAT Collaborations, Astrophys. J., 815 (2015) L23.[5] MAGIC Collaboration, Astron. Astrophys., 595 (2016) A98.[6] VERITAS, MAGIC Collaborations and NuSTAR, Astrophys. J., 819 (2016) 156.[7] MAGIC Collaboration, Science, 346 (2014) 1080.[8] MAGIC Collaboration, Astron. Astrophys., 589 (2016) A33.[9] Borla Tridon D. et al., in Proceedings ICRC 2011.[10] Mallot K. et al., TeVPa Conference, Tokyo (2015).[11] Colin P. et al., Proc. ICRC (2011).[12] IceCube, MAGIC and VERITAS Collaborations, JINST, 11 (2016) P11009.[13] Gora D. and Bernardini E., Astropart. Phys., 82 (2016) 77.[14] Gora D. et al., AIP Conf. Proc., 1792 (2017) 060008.[15] MAGIC Collaborations et al., Phys. Lett. B, 668 (2008) 253.[16] Doro M., EPJ Web of Conferences, 136 (2017) 01003.6 M. DORO[17] Doro M., in Proceedings of the 25th European Cosmic Ray Symposium (ECRS 2016), 4–9September 2016, Turin, Italy, CNUM: C16-09-04.3.[18] Particle Data Group (Patrignani C. et al.), Chin. Phys. C, 40 (2016) 100001.[19] MAGIC Collaboration, GCN #18776.[20] CTA Consortium, Exp. Astron., 32 (2011) 193.

Gamma-ray, particle and exotic physics at TeV energies with the MAGIC telescopes

MAGIC is an instrument composed of a pair of telescopes for gammaray and cosmic-ray astrophysics in the TeV range. It is operating for more than a decade now, and is one of the current best performing instruments in this ﬁeld, speciﬁcally at low energies, where it achieves the largest sensitivity. MAGIC pursues a strong program in galactic and extragalactic gamma-ray science. Its catalog of blazars, radiogalaxies and galaxy clusters observations as well as supernovae, novae, pulsar wind nebulae, pulsars and binary systems has now increased to several tens of detected targets. In addition, MAGIC is suited for cosmic ray searches, being sensitive to the signatures of earth-skimming tau-neutrinos, cosmic antiprotons, and others. Furthermore, MAGIC has a strong fundamental physics program, with searches for particle dark matter, Lorentz Invariance violations, axion-like particles and primordial black hole evaporation, providing important recent constraints in some relevant cases. Finally, MAGIC has a follow-up program of Gravitational Waves events. Few highlights topics will be discussed in this contribution

Scientific Open-access Literature Archive and Repository

DOI 10.1393/ncc/i2017-17115-5Colloquia: SciNeGHE 2016IL NUOVO CIMENTO 40 C (2017) 115Gamma-ray, particle and exotic physics at TeV energieswith the MAGIC telescopesM. DoroUniversità e Sezione INFN - Via Marzolo 8, I-35131 Padova, Italyreceived 21 April 2017Summary. — MAGIC is an instrument composed of a pair of telescopes for gamma-ray and cosmic-ray astrophysics in the TeV range. It is operating for more thana decade now, and is one of the current best performing instruments in this field,specifically at low energies, where it achieves the largest sensitivity. MAGIC pursuesa strong program in galactic and extragalactic gamma-ray science. Its catalog ofblazars, radiogalaxies and galaxy clusters observations as well as supernovae, novae,pulsar wind nebulae, pulsars and binary systems has now increased to several tensof detected targets. In addition, MAGIC is suited for cosmic ray searches, beingsensitive to the signatures of earth-skimming tau-neutrinos, cosmic antiprotons, andothers. Furthermore, MAGIC has a strong fundamental physics program, withsearches for particle dark matter, Lorentz Invariance violations, axion-like particlesand primordial black hole evaporation, providing important recent constraints insome relevant cases. Finally, MAGIC has a follow-up program of GravitationalWaves events. Few highlights topics will be discussed in this contribution.IntroductionMAGIC (Major Atmospheric Gamma-ray Imaging Cherenkov) is a telescope com-posed of a couple of 17 m diameter reflector of the IACTA (Imaging AtmosphericCherenkov Telescope Array) class. The technique is based on the observation of theCherenkov radiation generated in extended particle showers produced in the atmosphereby either cosmic particles of high energy cosmic radiation reaching the Earth. The sam-pling of the Cherenkov radiation guarantees good sensitivity, low energy threshold, goodenergy and angular resolutions, compared to shower-front particle detectors, at the ex-pense of a duty cycle limited to dark or moderate moonlit nights. MAGIC is located atthe Canary Island of La Palma (Spain), in the northern hemisphere, at the Observatoriode Roque de Los Muchachos, which will be soon hosting the new IACTA generationof the CTA project. The energy working range is 50 GeV to 50 TeV, with a sensitivityof 0.66% of the Crab Nebula flux above 220 GeV in 50 h [1] and the instrument is inoperation for a decade now.Creative Commons Attribution 4.0 License (http://creativecommons.org/licenses/by/4.0) 12 M. DOROFig. 1. – Science cases with very high energy gamma rays with MAGIC.The MAGIC science program is wide (see fig. 1), and focused on VHE gamma-rayastrophysics. This encompasses relativistic jets physics, plasma physics, magnetic re-connection, diffuse shock accelerations, cosmic ray transport and so on, requiring oftenstrong interdisciplinarity. The science pursues can be done in multiple galactic and ex-tragalactic targets and target classes. This will be discussed in sect. 1. However, withnon standard reconstruction algorithm, MAGIC can be operated as a particle detector,in the sense that it can discriminate cosmic particles: protons, electrons, etc. This isthe topic of sect. 2. Finally, MAGIC has the characteristics to be sensitive to someNew Physics scenarios, including dark matter and Lorentz Invariance violation, but also(if existing) to electromagnetic counterparts of gravitational wave events. These will bediscussed in sects. 3 and 4, respectively.Due to space limitation, this contribution will be a brief overview. More detailedreports on MAGIC physics and the success of IACTA can be found for example in [2,3].1. – MAGIC as a TeV gamma-ray detectorThe presence of VHE (Very High Energy: > 100GeV) gamma rays in astrophysicalenvironment is always connected to parent highly accelerated cosmic ray particle (lep-tons and/or hadrons). Therefore gamma ray astrophysics probes cosmic ray physics.However, to be able to understand the particle and radiation fields in astrophysical en-vironments, a large astronomical framework of knowledge is required, formed by a widemulti-wavelength and multi-instrument contribution. Classical targets for VHE gamma-ray observations were mentioned in the abstract. It is impossible to summarize the manyresults achieved with observation at VHE in the past decade. Only a selection will bediscussed, in which MAGIC has shown unique capabilities.The low MAGIC energy threshold (50 GeV), had allowed to search for the farthestsources in the sky, because of the opaqueness of the Universe to VHE gamma rays lostdue to pair production with the UV-IR background radiation fields of the ExtragalacticBackground Light (EBL), the second radiation field permeating the universe after theGAMMA-RAY, PARTICLE AND EXOTIC PHYSICS AT TeV ENERGIES ETC. 3Cosmic Microwave Background (CMB). MAGIC has recently expanded the TeV universeby doubling the distance of the farthest sources known. Two sources at redshift z ∼ 1were detected [4, 5]: the galaxy PKS 1441+25 at z = 0.939 and the galaxy B0218+35at z = 0.944 of which MAGIC did not observe the direct light, but that gravitationallylensed from an intervening spiral galaxy in between. This was the first gravitational-lensed delayed VHE signal ever observed.The importance of multi-wavelengths campaign has become utter, and indeed MAGIChas developed several monitoring campaigns and Time of Opportunity programs basedon external triggers. For example, during the Mrk421 campaign reported in [6], thesource had the coverage of Swift-UVOT, Swift-XRT, NuSTAR, Fermi LAT, MAGIC,and VERITAS. The flare event not only generated an increased flux, but also shiftedthe emission peak toward higher energies. In the Synchroton Self-Compton scenarios,this may hint to a different (than baseline) electron population that was swept-up or onesingle electron population that was boosted for some mechanism. The energy-dependentvariability provided an important part of the puzzle of the global picture of the targetdynamics. The flares in Active Galactic Nuclei (AGNs) provide useful insights into theassociated Black Hole (BH) physics. All kinds of AGNs in MAGIC catalog have shownextremely fast variability. In 2014, MAGIC saw an impressive flare of the radio-galaxyIC 310. The flux doubled in 4.8 minutes, from an object located at 78 Mpc. It isvery unclear what mechanisms could provide such boost because rise-time constraintsemission size: the emission region must have a size smaller than the 20%of the BHsize. The proposed explanation is that particle acceleration occurs by the electric fieldacross a magnetospheric gap at the base of the radio jet, much alike the pulsar radiationmechanism [7].Galaxy clusters are expected to show a diffuse gamma-ray emission due to the inter-action of accelerated CR with the ambient intracluster medium. Perseus (78 Mpc far) isa cool-core clusters, the brightest in X-ray and thus an optimal lab to search for gammarays associated to accelerated particle fields in the core. The explanation for the origin ofradio halos is in fact challenging and TeV gamma-ray are an unique probe. TeV gammarays are expected in hadronic model because radio-emitting electrons are secondaries pro-duced by CR protons interacting with the protons of the ICM, or in re-acceleration modelwhere seed population of CR electrons are re-accelerated by interacting turbulent waves.MAGIC observed for 250 h (selected) in 4 years, providing several (model-dependent)constraints. With MAGIC data, we constrained the fraction of the energy dissipated instructure formation shocks that goes into particle acceleration to be not larger than 37%.We limited the cosmic-ray to thermal-pressure ratios to values between 2 and 20%. Weconstrained the magnetic fields that produce the observed synchrotron emission fromsecondary electrons to be smaller than 10 μG [8].Other recent MAGIC results are available here: https://magic.mpp.mpg.de/backend/results/latest.2. – MAGIC as a TeV particle detectorBesides cosmic gamma rays, atmospheric showers are initiated by cosmic rays. Actu-ally, the number of showers generated by the latter class is more than a factor of thousandlarger than those initiated by gamma rays. The ability of IACTA to discriminate betweengamma and particles, and among particles, stems mostly from the different imprint inthe camera produced by different primaries. MAGIC is routinely used as a particle de-tector. It can perform all-electron searches [9, 10], but in principle can also discriminate4 M. DOROthe charge of the particle by using the shadow of the Moon [11]. MAGIC also follows uptriggers from High Energy events from the IceCube neutrino detector [12].In the following, we focus on the preliminary results MAGIC achieved on the capabilityto discriminate cosmic tau-neutrinos events in the data, thus opening the possibility ofMAGIC as a neutrino detector. This challenging method is based on the fact thatMAGIC, from its mountain location, has a “window of visibility” of 80 × 5 deg2 inthe direction of the Atlantic Ocean, at zenith angles slightly below 90◦. The Ocean isabout 170 km away. By pointing the telescope in this window, MAGIC could detectatmospheric shower generated by tau-leptons emerging from the ocean’s surface, andsoon-after decaying and generating particle showers. In turn, this very energetic tau-lepton (the accessible energy range is beyond the PeV), must have been produced not toodeep inside the ocean by the conversion of a very energetic cosmic tau-neutrino enteringthe Earth in the same MAGIC observing direction. The technique is discussed in [13](and references therein). Tau-induced showers are discriminated because they are createdmuch closer to the telescope compared to any other possible source of background [14].Although the sensitivity to these signals is in principle rather high for MAGIC, at the levelof even above that of IceCube above the PeV range, the prospects for actual detectionof cosmic tau-neutrinos are still thin, due to very low expected flux. This may not bethe case in the occurrence of a strong flare (of an AGN, or a gamma ray bursts, or froma gravitational wave event) where hadrons are expected to be strongly accelerated, thusproviding also an ample neutrino flux. In this case, if the source passed through the“ocean window”, the neutrino flux can be indirectly observed. This observation mode isstill under development in MAGIC. However, even null observation from a flaring sourcecould provide interesting upper limits on the amount of tau-neutrino produced locally,competitive to other instruments in the field.3. – MAGIC as a New Physics detectorThere are many theoretical arguments indicating that there may be new Physicsaround the TeV scale. IACTA could be valuable probes for Lorenz Invariance Violations,by observing the time-of-flight delays of photons at difference energy, a tiny effect pos-sibly amplified by the cosmological distances at hand [15]; IACTA can probe Axion-likeParticles (ALPs), that may explain the otherwise awkward observation of TeV photonsfrom targets where we expect photons should be hardly observable, because of absorb-ing medium either located at the source (e.g. dense gas fields) or in the path to thesource. By converting to ALP, faraway TeV photons could thus travel larger distancesthan expected. IACTA can see gamma-ray flashes from fast evaporating Black Holesgenerated in the early Universe and evaporating in these times; finally, the passage ofexotic objects like magnetic monopoles or quark nuggets, could also generate Cherenkovlight observable with MAGIC (see recent review [16]).However, large attention is paid to IACTA for their capability as dark matter (DM)detectors. They are indeed valuable DM probes, for the following reasons: a) it is oftenthe case that gamma rays are found in prompt annihilation or decay reaction in DM richenvironment, b) the associated gamma ray spectrum, for many DM scenarios, can peakat the TeV and may present peculiar features that can easily differentiate it from a purelyastrophysical one, c) DM spectra would be universal, so several different targets may beobserved with exactly the same spectra, d) the shape of the spectra and its cutoff at theDM mass provide also clues for identification of DM besides detection. DM searches aredone with MAGIC at several targets (see a recent review [17]). The cleanest targets inGAMMA-RAY, PARTICLE AND EXOTIC PHYSICS AT TeV ENERGIES ETC. 5the sky are the dwarf galaxies gravitationally bound to the Milky Way and orbiting itsthe DM halo. These are small galaxies, with almost no stellar activity, where DM musthave accreted in large concentrations (mass-to-light ratios thousands of times that of theSun), as seen by stellar velocity dispersion. MAGIC has a large track in observing theseobjects. The recent large campaign (160 h) on the Segue 1 satellite galaxies provided thestrongest constraints from this class of targets above few hundreds of GeV, and receivedthe attention of the Particle Data Group [18].4. – MAGIC as a GW counterpart detectorGravitational waves (GWs) associated physics has recently gained a strong interestdue to multiple detections of GWs by the Ligo Virgo Collaboration (LVC). Although thetheoretical mapping is far from being complete, it is believed that if the merger eventhappen between at least one compact object (NS-NS or NS-BH mergers), a measurablegamma-ray counterpart may be expected, although its spectral energy distribution isunclear. MAGIC can rapidly reposition (< 20 sec) after receiving a GW alert from LVC.However, its small field of view (about 10 square degrees) cannot sample but a smallfraction of the LVC region of interest. Despite so, MAGIC has performed follow-ups ofGW161226 [19] and is refining its strategies toward a better selection of pointings.5. – ConclusionsAlthough not the mainstream science, among the MAGIC science goals is that oftrying to add a piece in the puzzle of cosmic ray fluxes at Earth, hunting elusive tau-neutrinos, finding signatures of New Physics. The astrophysical results are disparate, andfrom tens of of targets and target classes. Result are now contributing to astrophysics in awide multi-instruments and multi-wavelengths scenarios, placing gamma-ray astrophysicsinto the realm of a true astronomical field. MAGIC has contributed in many ways to thissuccess along the past 12 years. Few years ahead will be productive until the times comefor the future generation of instruments in this field, with the Cherenkov Telescope Arrayobservatory [20] already in construction close to MAGIC at the island of La Palma.REFERENCES[1] MAGIC Collaborations, Astropart. Phys., 72 (2016) 76.[2] Lorenz E. and Wagner R., Eur. Phys. J. H, 37 (2012) 459.[3] Aharonian F. et al., Rep. Prog. Phys., 71 (2008) 096901.[4] MAGIC and Fermi LAT Collaborations, Astrophys. J., 815 (2015) L23.[5] MAGIC Collaboration, Astron. Astrophys., 595 (2016) A98.[6] VERITAS, MAGIC Collaborations and NuSTAR, Astrophys. J., 819 (2016) 156.[7] MAGIC Collaboration, Science, 346 (2014) 1080.[8] MAGIC Collaboration, Astron. Astrophys., 589 (2016) A33.[9] Borla Tridon D. et al., in Proceedings ICRC 2011.[10] Mallot K. et al., TeVPa Conference, Tokyo (2015).[11] Colin P. et al., Proc. ICRC (2011).[12] IceCube, MAGIC and VERITAS Collaborations, JINST, 11 (2016) P11009.[13] Gora D. and Bernardini E., Astropart. Phys., 82 (2016) 77.[14] Gora D. et al., AIP Conf. Proc., 1792 (2017) 060008.[15] MAGIC Collaborations et al., Phys. Lett. B, 668 (2008) 253.[16] Doro M., EPJ Web of Conferences, 136 (2017) 01003.6 M. DORO[17] Doro M., in Proceedings of the 25th European Cosmic Ray Symposium (ECRS 2016), 4–9September 2016, Turin, Italy, CNUM: C16-09-04.3.[18] Particle Data Group (Patrignani C. et al.), Chin. Phys. C, 40 (2016) 100001.[19] MAGIC Collaboration, GCN #18776.[20] CTA Consortium, Exp. Astron., 32 (2011) 193.

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Gamma-ray, Particle and Exotic Physics at TeV energies with the MAGIC telescopes

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