Dr. Nicolò Masi Bologna University and INFN – November 13th 2015 Knowledge and Prejudices

Hard to question that:

• Non-gravitational interactions between DM and Standard Model particles are highly suppressed: the lack of observations disfavors DM that is electrically charged or interacts by the strong nuclear force. • It was called “dark” by F. Zwicky in 1933, long before the underground experiments and the direct detection studies that are testing also its interactions with fermions. • DM must clump gravitationally to form . This requires DM to be “cold”, that is non- relativistic at the time of . • The theoretically best-motivated candidates for a DM particle are a weakly interacting massive particle (WIMP) or an or axion-like particle (ALP). • WIMPS could solve the Hierarchy problem whereas an axion solves the Strong CP problem of the Standard Model. Typically WIMPs are considered to be thermal relics left over from the Early ; ALPs are usually not thermal. • We will focuss on the WIMP case, because we have less and more controversial evidences about axion-like particles properties. And because WIMPs are the most suitable candidates for direct and indirect searches.

Nicolò Masi, 13/11/2015, DM State of Art • The abundance today is inversely proportional to the WIMP self-annihilation cross section. The fractional abundance, relative to the critical density, and the thermal averaged annihilation cross section are

We believed that: 휎푣 ≈ 3 ∙ 10−26푐푚3푠−1 is a typical value expected for a particle with mass near the weak scale [O(100 GeV)] and a weak gauge coupling: the fact that the observed abundance of DM points to new physics at the weak scale, independently of particle physics motivations, is the so-called WIMP miracle (a Naturalness Criterion). But • Any combination of 푚퐷푀, 푔푋 can be taken. • The only real bound is that the DM must be relatively “light” as a consequence of the existence of a maximum annihilation cross section for a particle of a given mass: the so-called Unitarity Bound. • Griest and Kamionkowski applied this bound to infer an upper limit on the dark particle mass: using PLANCK constraints, this bound is something like: mDM ≲ 120 TeV (for a scalar). It slightly varies according to the spin-statistics of the candidate. A recent study shows a mDM ≲ 139 TeV constraint for a Dirac fermion. • Run I LHC researches excluded DM candidates up to 600 GeV-1 TeV scale.

Nicolò Masi, 13/11/2015, DM State of Art Prejudices

Some well spread paradigms, or “theoretical prejudices”:

1. DM has a zero electromagnetic cross section (some theories try to overcome the charge issue introducing a milli-charge or electric/magnetic dipole moments, conserving the main dark behavior of the particle). But, at the same time, it is capable to collide with our visible world particles. 2. DM particles are thermal relics which produce the EW scale Miracle. A not too heavy SUSY particle was the perfect candidate. 3. DM is made of one particle and resembles usual Standard Model “simplest” particles, stable and not affected by Standard Model-like anomalies and violations: some asymmetric theories try to overcome this simplification. 4. DM is much more a particle (a Majorana from SUSY inheritance) than a force, i.e. a real boson. 5. DM forms “simple” spherical halos around galaxies, without important substructures. This is a dangerous assumption when we have to deal with simulations of cosmic rays (CR) fluxes and with recoil physics in direct detection experiment (a Dark Disk can change everything!). Eur. Phys. J. Plus (2015) 130: 69 Nicolò Masi, 13/11/2015, DM State of Art Galactic Evidences Local Galactic Evidences 1. Rotation Curves From the Kepler’s law, for r much larger than the luminous radius, you should have v ∝ r-1/2: instead it is flat or rises slightly.

Milky Way 2015

Mgrav : Mvis = 8÷6 : 1

Nicolò Masi, 13/11/2015, DM State of Art 2. Velocity dispersions of dwarf spheroidal galaxies

Not only spiral galaxies evidences

Nicolò Masi, 13/11/2015, DM State of Art 3. warp and dark galaxies Milky Way like a long play record

…But Magellanic Clouds don’t explain the entire Warp Factor problem. • With the Sloan Digital Sky Survey a lot of low-brightness satellites galaxies have been discovered, but not enough to account the whole dynamical Milky Way warp: there should be tens of almost dark galaxies. • This is known as “the dwarf problem”: in the Universe there are 10 to 100 times fewer small galaxies than predicted by dark matter theory of galaxy formation and spiral galaxies warp.

The solution: VIRGOHI21

VIRGOHI21 is an extended region of neutral hydrogen (HI) in the Virgo Cluster discovered in 2005. Analysis of its internal motion indicates that it may contain a large amount of DM, as much as a small galaxy, but no stars: the first .

Nicolò Masi, 13/11/2015, DM State of Art Cosmic Evidences Cosmic Evidences 1. Dynamics of galaxy cluster

Virial theorem

U = 2K 2 K = i mi vi U ~ GM2/R

• The Bullet cluster (1E 0657-56) consists of two colliding clusters of galaxies. At a statistical significance of 8σ, it was found that the spatial offset of the center of the total mass from the center of the baryonic mass peaks cannot be explained with an alteration of the gravitational force law. It provides "evidence against some of the more popular versions of Modified Newtonian Dynamics (MOND)" . • In other words: The lensing is strongest in two separated regions near the visible galaxies. This provides support for the idea that most of the mass in the cluster pair is in the form of collisionless dark matter. Nicolò Masi, 13/11/2015, DM State of Art 2. X-ray cluster

The mass of a cluster can be determined via the profile of X–ray emission that traces the distribution of hot emitting gas in rich clusters

Hydrostatic equilibrium:

Beta model:

Estimated Temperature:

The disparity between the temperature of the previous formula and the corresponding observed temperature, T ≈ 10 keV, when Mr is identified with the baryonic mass, suggests that Mgrav/Mvis ~ 15

Nicolò Masi, 13/11/2015, DM State of Art 3. Lensing

Weak Lensing: the distortions are small and can only be detected by analyzing large numbers of sources to find coherent distortions of only a few percent. COSMOS 3D DM distribution from 3.5 to 6.5 billion years ago.

Strong Gravitational Lensing: there are easily visible distortions such as the formation of Einstein’s rings, arcs and multiple images.

4퐺푀 Deflection Angle 휃 = 푟푐2

Nicolò Masi, 13/11/2015, DM State of Art 4. DM Skeleton between galaxies

Galaxy clusters occur at the intersection of large-scale structure filaments. The thread-like structure of this “cosmic web” has been traced by galaxy redshift surveys for decades.

The COSMIC DM WEB

Contour lines outline an invisible dark matter filament connecting the galaxy clusters Abell 222 (bottom) and Abell 223 (top) in the night sky.

Nicolò Masi, 13/11/2015, DM State of Art Planes (2014): the discovery of symmetric structures in the

Great spiral galaxies Spiral galaxies have their form on the main nodes satellites confined in a plane, of the Cosmic DM Web orthogonal to their own luminous one, which seems to follow the ingoing filaments

Milky Way

Dwarf Galaxies

Nicolò Masi, 13/11/2015, DM State of Art Cosmological Evidences Cosmological Scale Evidences: 1. PLANCK Acoustic Peacks

Universe Curvature

Baryon density

Matter density

Nicolò Masi, 13/11/2015, DM State of Art Planck Pie Chart

Perfect Λ퐶퐷푀 scenario

Nicolò Masi, 13/11/2015, DM State of Art 2. Baryonic Oscillation, Structure Formation and Evolution

• Acoustic Oscillations (BAO) refers to regular, periodic fluctuations in the density of the visible baryonic matter of the universe, caused by acoustic primordial waves. • In the same way that SNe Ia provide a “standard candle" for astronomical observations, BAO matter clustering provides a “standard rules" for length scale in cosmology.

The scale of BAO depends on 휴풎: one can quantify the amount of dark matter on very

large scales: Ω푏 Ω푚 = 0.155 ± 0.006.

Furthermore, galaxies could not have formed from primordial density fluctuations in a purely baryonic medium.

Nicolò Masi, 13/11/2015, DM State of Art Not a particle? Modified Newtonian Dynamics (MOND) is a MOND hypothesis that proposes a modification of Newton’s law of gravity/second law to explain the galaxy rotation term

Milgrom’s idea: the acceleration due to gravitational force depends upon the

function μ(a/a0), which approaches 1 for Newtonian cases and a/a0 for small arguments. −10 2 (a0 ≈ 10 m/s ) The velocity of stars on a circular orbit far from 4 the center is a constant and does not depend 푣 = 퐺푁푀푎0 on the distance r → the rotation curve is flat

 The AQUAL and TeVes Lagrangian generalizations were developed by Milgrom and Bekenstein.  Studies of the aforementioned Bullet Cluster (August 2006-2008) provide evidence against some of the more popular versions of MOND.  In addition, an important 2011 study observing the gravity-induced redshift of galactic clusters found results that strongly supported General Relativity: MOND can fit the determined redshifts slightly worse than does General Relativity with dark halos. Nicolò Masi, 13/11/2015, DM State of Art With Modified Gravity (MOG) several theories MOG which introduce new cosmological fields are addressed, starting from a tensor generalization of Einstein Gravitational Theory.

• MOG has evolved as a result of investigations of Nonsymmetric Gravity Theory (NGT) and, most recently, it has taken the form of Scalar-Tensor-Vector Gravity (STVG), that extends Einstein-Hilbert action using new scalar, tensor, and vector fields and new constants above the Newtonian one.

• Einstein gravity coupled to massive fields leads to an acceleration law that modifies the Newtonian law of attraction with a Yukawa-like term, generating a running of the effective gravitational coupling GN and an increase of it at large galactic distances:

Nicolò Masi, 13/11/2015, DM State of Art Gravity theories which are invariant under conformal (Weyl) transformation: Conformal Gravity 2 푔푎푏 Ω (푥)푔푎푏

• The simplest theory in this category has the square of the Weyl tensor as the Action: 1 푆 = 푑4푥 −푔퐶 퐶푎푏푐푑 = 2 푑4푥 −푔(푅 푅푏푑 − 푅2) 푎푏푐푑 푏푑 3

• The solution for a massive 4-derivative wave equation, in a central field of force, is:

2푚 Φ 푟 = 1 − + 훼푟 + 훽푟2 푟 • The last two terms are unique: it has been suggested to assign small values to them to account for the Dark Matter effects and the . No new physical fields are added. • The cons are that there may be issues with causality: presence of ghosts (or at least caustic formation) which point to instabilities of the quantum version of the theory.

Nicolò Masi, 13/11/2015, DM State of Art The main idea: to make the effective Non-Local Gravity Newton constant depend on the frequency and wavelength, i.e. on the scale.

• Analogs in electromagnetism are frequency-dependent dielectrics.

• The modifications of the Einstein-Hilbert action are non-local and acausal:

Modified Einstein Equations

푒푓푓 ℱ(□) is the d’Alambertian (8π퐺 )−1 퐺 = 푀2 (1 +ℱ(□)) 퐺 = 푇 푁 휇휈 푃푙 휇휈 휇휈 scale “filter function”

• The scale dependent gravitational coupling introduces a General Relativity with a running for 푮푵. The theory can be implemented adding some dynamically dependent terms. • For Barvinski’s point of view, the usual Ricci scalar action is substituted with a scale dependent one:

• A class of generally covariant ghost-free nonlocal gravity gains a mechanism of DM simulation. Nicolò Masi, 13/11/2015, DM State of Art Non-particle Gravity Theories MOND MOG Conformal Gravity Non-local Gravity… = Phantoms, 4°-derivative theories, acausal, not capable to reproduce all the observations, especially the cosmological ones, i. e. CMB and BAO physics and structure formations.

A consistent particle dark matter apparatus seems to be mandatory, in the absence of a full quantum-gravity theory

Nicolò Masi, 13/11/2015, DM State of Art If it exists: how to detect DM

3 2

1

Nicolò Masi, 13/11/2015, DM State of Art •

• The possibility to detect the recoil energy of the nuclei of a low–background detector as a consequence of their elastic scattering with a WIMP. • The signal arises if the solar system itself is moving relative to the stationary halo of WIMP as it orbits around the Milky Way center.

This recoil can be detected in some ways:  Electric charges released (ionization detector)  Flashes of light produced (scintillation detector)  Vibrations produced (phonon detector) Elastic cross section (SI):  Phase Transition Nuclear Form Factor Differential Recoil Integral over local Energy Spectrum WIMP velocity distribution Nicolò Masi, 13/11/2015, DM State of Art The scalar interaction scales with a power of the the atomic weight and almost always dominates for nuclei with A > 30.

Nicolò Masi, 13/11/2015, DM State of Art It won’t be forever

/H

LUX currently holds the leader position for DM masses above 6 GeV; Xenon has already prepared a nuclear response in the form of a ton detector. Meanwhile, the SuperCDMS experiment will secure a monopoly in the low-mass region.

Direct detection experiments will inevitably hit the neutrino wall: they will reach the sufficient sensitivity to observe nuclear recoils due to elastic scattering of solar and atmospheric neutrinos. That will constitute an irreducible background to dark matter searches (unless directional detection techniques are developed). There are also stringent bounds from IceCube for the Spin-dependent DM cross-section….

−(ퟒퟏ÷ퟒퟎ) ퟐ 흈푺푫 < ퟏퟎ 풄풎

The principle: WIMPs could be gravitationally captured by massive objects like the Sun and accumulate in the core the Sun itself: for high enough density they would annihilate producing neutrinos, which could be observed by IceCube  Look for missing energy signatures.  Problem: Can only find DM candidate (no proof that it is DM)

CMS Results

Nicolò Masi, 13/11/2015, DM State of Art Other Interaction Cross Section Limits: Photons and Neutrinos

Is it correct to say it is «dark»? 휎훾−퐷푀 from Cosmology Using Planck TT and BB spectrum along with Lyman-α measurements and structure formation consideration we can put constraints on DM interactions with 훾 and 휈: • For TeV-ish DM large cross sections with photons are allowed • A stronger result could be achieved using future Planck polarisation data • One can use cosmological data to study DM interactions independently of any theoretical prejudice

−ퟑퟔ ퟐ −ퟑퟎ ퟐ 2014 흈휸,흂−푫푴 < ퟏퟎ 풄풎 − ퟏ 푴풆푽 푫푴 흈휸,흂−푫푴 < ퟏퟎ 풄풎 − ퟏ 푻풆푽 푫푴

휒푁 −(45÷44) 2 Direct Constraints 휎푆퐼 < 10 푐푚 XENON100 + EDELWEISS + ICECUBE: 휒푁 −(41÷40) 2 휎푆퐷 < 10 푐푚

Current DM is more weakly- SI dark matter-nucleon cross section is 4÷5 orders of magnitude beneath the neutrino’s interacting than dark? one for a solar 10 MeV neutrino:

Nicolò Masi, 13/11/2015, DM State of Art Annihilation Cross Section Constraints Annihilation Cross Section Constraints

Many observations point to a TeV-ish DM with a boosted annihilation cross section of the order of ~10−23푐푚3 ∙ 푠−1

IceCube (IC) neutrinos limits obtained in the μ+μ− channel compared to preferred regions from PAMELA and Fermi, along with VERITAS limits for Segue 1, H.E.S.S. limits for the Fornax galaxy cluster, Fermi for stacked dwarf galaxies and the Fornax cluster.

Nicolò Masi, 13/11/2015, DM State of Art Planck CMB vs AMS-02 indirect searches

arXiv:1509.00058

푓푒푓푓 = 0.1, 0.15, 0.2 CR propagation uncertainties, DD hypothesis, pulsars contributions, alternative CR propagation models Literature best-fits

• Allowed parameters space for indirect search from AMS-02/Fermi/PAMELA (rectangles), along with Planck 2015 bound (blue line). • Only a Cosmic Variance Limited (CVL) experiment (yellow line) could completely falsify

the CR indirect search constraints for TeV-ish candidates. Nicolò Masi, 13/11/2015, DM State of Art

The AMS-02 Detector • Dimensions: 5x4x3 m3 • Acceptance: 0.45 m2 sr • B: 0.15 Tesla • Redundancy

ACC

38 Nicolò Masi, 13/11/2015, DM State of Art Mission duration: through the lifetime of the ISS, until 2024 or longer 39 Nicolò Masi, 13/11/2015, DM State of Art TOF ultimate performances in space: Beta/time, position and charge

Carbon Beta Resolution: 1.2% --> 48 ps (electronic limit)

Longitudinal TOF-Tracker coordinate measurements

40 Nicolò Masi, 13/11/2015, DM State of Art TOF continuous charge distribution for all ions detected by AMS-02 up to Zn

• Charge measurements with dynodic PM signal up to Z=30

• The resolution increases with Z, reaching, after Z = 2, a constant term of about 1 %, corresponding to a resolution in time better than 50 ps

41 Nicolò Masi, 13/11/2015, DM State of Art Apparent charge of electrons selected by TRD and ECAL

The number of particles hitting the TOF counters increases as the layer 1 electron penetrates deeper in the layer 2 detector producing more particles through brehmstrallung. layer 3 layer 4 These events may suffer of a bad rigidity measurement due to wrong association of tracker hits to two the reconstructed track. particles three The TOF information can be used particles in the computation of a likelihood function, which contribute in identifying charge-confusion events.

Nicolò Masi, 13/11/2015, DM State of Art How we can see DM in our Galaxy: Cosmic Rays Anomalies

…WIMP Dark Matter self-annihilates in the and injects into CRs detectable products: 훾, 휈, 푒+, 푝 , 푑 . They progate in the Milky Way, according to a Standard Model, and arrive at the top of the atmosphere. Before AMS: PAMELA Anomaly

Antiproton Channel Positron Channel

New Physics?

A perfect secondary We have to explain spectrum: No Dark Matter Signal this tension 44 Nicolò Masi, 13/11/2015, DM State of Art The Sommerfeld Enhancement/Boson

Feynman diagram of Sommerfeld cross section boost

Leptophilic

Inadequate production for < 1÷2 TeV WIMP: to grant PAMELA results we need heavier candidates and high boost associated to a 1÷100 GeV S boson: new antiproton physics for AMS-02 in the 150 GeV - 2 TeV range for MDM < 10 TeV

Nicolò Masi, 13/11/2015, DM State of Art AMS-02 antideuteron search

AMS-02 sensitivity: 10^-6

AMS-02 will be approximately an order of magnitude less constraining than the future GAPS

Nicolò Masi, 13/11/2015, DM State of Art Dark Matter Candidates in the post-Higgs Era The Dilemma: a great desert

Nicolò Masi, 13/11/2015, DM State of Art Summary: Heavy Candidates for AMS-02

SUSY Wino M = 1 TeV 푝 Neutralino

푒+ KK Universal Extra Dimension (UED) vector boson Spin-statistic - dirac or majorana fermion, boson: Little Higgs S = 0,1/2, 1, 3/2, 2…but we Scalar massive photon prefer self-annihilating Multiplet 100 1000 candidates 푒+ 푒+

M = 1.5 TeV

Nicolò Masi, 13/11/2015, DM State of Art Theoretical Uncertainties: background removal for indirect DM searches

What we are doing in Bologna… Fluxes uncertainties: astrophysics vs dark halo

Rescaled antiproton DM halo ratio: flux Einasto vs NFW

1. Propagation models: almost two orders of magnitude, one above one below the MED set 2. Radial distribution of the halo: modulates spectra in a less significant way, even if higher DM density regions in the inner Galaxy or the introduction of a cohorotating Dark Disk could induce a greater annihilation cross section. 51 Nicolò Masi, 13/11/2015, DM State of Art Nuclear Uncertainties: DM annihilation cross section constraints from PAMELA and an AMS-02 data projection

Reference band 풑 for fitting function (to NA49 data)

20÷40% uncertainty

퐸퐾

푝 + 푝 푝 … 푝 + 퐼푆푀 푝 … 푝 + 퐻푒 푝 …

Nicolò Masi, 13/11/2015, DM State of Art Flux uncertainty for 푝 from the dark sector physics

Annihilation channels ratio: NLO corrections to the primary DM flux bottom (b) vs up/down (q) vs vector boson (W)

푒+ 푝 1 o.f.m.

Simulazions based on PPPC 4 DM ID (Cirelli, Kadastik, Strumia et al.)

Uncertainties linked to DM physics are hard to be removed, but they are still lower than the fundamental uncertainty which afflicts the cosmic rays propagation physics

Nicolò Masi, 13/11/2015, DM State of Art MonteCarlo Markov Chain Approach: full parameters scan with AMS multiple constraints from CRs

What we are doing in Bologna… Dark matter physics in the 푝 푝 channel

1. Fitting AMS-02 nuclear data with Monte-Carlo-Markov-Chain methods applied to GALPROP for K>10 GeV/n, a propagation scheme has been achieved 2. With this single set of propagation parameters, we can describe all the CR phenomenology, from heavy nuclei to protons and antiprotons 3. Once fixed the propagation parameters we have removed the secondary background for DM searches in the 푝 푝 channel

. MCMC iterative procedure is used to sample GALPROP cosmic rays propagation parameters

. The CosRay-MC software we implemented in Bologna (developed from COSMOMC package) can be run @ CNAF: tens of thousands simulations in few days

Nicolò Masi, 13/11/2015, DM State of Art Results: Spectra and Ratios Fits (solar modulation 550-600 MV)

Protons Helium

AMS-02 published/ICRC Data GALPROP Simulation H/He

B/C

56 Nicolò Masi, 13/11/2015, DM State of Art MCMC Matrix With p, He, B/C, and preliminary Boron, Carbon, Oxygen spectra from AMS-02 we can easily constrain, for the first time, the fundamental parameters that describe the CR propagation

and the galactic physics

Number Number

5 5 of of trials (log scale) 4 of trials (log scale) 4

3 3

2 2

1 1

0 0

훾2 Number

5 5

4 of trials (log scale) 4 3 3

2 2

1 1 0 0 Nicolò Masi, 13/11/2015, DM State of Art CR Physics Improvements Before AMS-02 After AMS-02

Improvement Error (%) Unit Error (%) factor 휺풃풆풇풐풓풆 휺풂풇풕풆풓 풛 kpc 54% 4% 14 2 −1 6% 푫ퟎ/10^28 cm s 96% 16 휹ퟏ,ퟐ 57% 5% 11 −1 푽푨풍풇풗풆풏 km s 89% 11% 8 −1 푽ퟎ풄풐풏풗 km s 100% 10% 10

−1 −1 풅푽푪 풅풛 km s 푘푝푐 100% 10% 10

. Past experiments were not able to fix the CR propagation physics: the parameters lied in very wide ranges. A factor 10 (or greater) . With AMS-02 data is finally possible to achive a consistent of improvement for best fit: the errors associated to the fundamental fundamental parameters propagation parameters 퐳, 푫ퟎ풙풙, 휹ퟏ,ퟐ are greatly reduced. . We still have some degeneracies/uncertainties which afflict secondaries predictions. Nicolò Masi, 13/11/2015, DM State of Art A natural implication

Applying this knowledge to antiprotons: 푝 푝 up-to-date predictions ICRC 2015

Nicolò Masi, 13/11/2015, DM State of Art Nicolò Masi, 13/11/2015, DM State of Art Error Bands: Propagation vs Nuclear physics

(ICRC 푝 푝 data)

. Nuclear and propagation uncertainties are comparable but in the high energy region the propagation error is lower than the nuclear one. . Adding further AMS data set to the analysis (C/O, C/He, O, Li, etc) the propagation error will be reduced. 62 Nicolò Masi, 13/11/2015, DM State of Art Propagation Uncertainty defined with the MCMC method

With the previously obtained propagation set we compute secondaries 푝 푝

Censored according to Collaboration policies

Best fit

Propag. Uncertainty

Solar Modulation effects are included in the 1휎 parameters band Nicolò Masi, 13/11/2015, DM State of Art Nuclear uncertainty band for uptodate cross section data

Censored according to Collaboration policies

푝 + 푝 푝 … 푝 + 퐼푆푀 푝 … 푝 + 퐻푒 푝 … From F. Donato estimate (arXiv:1408.0288)

64 Nicolò Masi, 13/11/2015, DM State of Art Total uncertainty band + DM DarkSUSY simulations

BETTER CANDIDATES: m > 1÷2 TeV, 0.6 TeV < m < 1 TeV and 휎푣 < 10−25푐푚3/푠

Censored according to Collaboration policies AMS last point

• TeV-ish candidates are favored by LHC, direct, indirect and astrophysical searches. • AMS-02 preliminary results are compatible with a secondary production but DM signals could hide within the overall error band. • With a nuclear effort we will be capable to extract a DM signal. Nicolò Masi, 13/11/2015, DM State of Art AMS-02 recent published results: how can we read them? Positron Fraction (0.5-500 GeV) Interpretation

275 ± 32 퐺푒푉

1. Sum of a diffuse spectrum and a single power law source

2. No clear sign of substructures

3. Isotropy: 훿 ≤ 0.030

4. Above ~250 퐺푒푉 the positron fraction no longer exhibits a remarkable increase with energy 67 Nicolò Masi, 13/11/2015, DM State of Art Electrons (0.5÷700 GeV) and Positrons (0.5÷500 GeV) fluxes

Positrons rise after 20 GeV incompatible with secondaries predictions

68 Nicolò Masi, 13/11/2015, DM State of Art Changes in the spectral indices of leptons fluxes: what is missing?

 Standard simulations with pure secondaries are not capable of reproducing positrons, without introducing primary DM or/and astrophysical components  Positrons (and electrons) spectra hardening above 30 GeV is not expected within the standard paradigms  The change of slope is very similar for electrons and positrons, with an approximately 69 + − conserved ∆훾푒 −푒 Nicolò Masi, 13/11/2015, DM State of Art Pulsars Problem

Anyone of two well-known nearby pulsars, Geminga and Monogem, can satisfactorily provide enough positrons to reproduce AMS-02 observations:

∆퐴푀푆≤ 0.030

The predicted anisotropy level is, at present, consistent with limits from Fermi-LAT and AMS-02

Nicolò Masi, 13/11/2015, DM State of Art A novel propagation configuration: The contributions to the positron fraction of all the leptons spectra are computed the 178 pulsars in the ATNF catalogue with assuming the extra-component d < 3 kpc fit AMS data very well: sources are located only in spiral arms.

Both the pulsar (nearby or altogether) and the DM scenarios can fit the observations: it is a fundamental problem to distinguish these two scenarios. If the positron excess is from pulsars, it may have a characteristic spectrum with many structures or steps, because the parameters of pulsars might differ from one to another. If such fine structures are not discovered, it would be a strong support to the DM interpretation. Nicolò Masi, 13/11/2015, DM State of Art B/C: preliminary hints

ICRC 2015

 The B/C ratio does not rise at high energies, up to about 700 GeV/n: SNRs reacceleration models are ill-favored  The antiproton channel for DM indirect search will represent the most significant signal of new particle physics, even cleaner and clearer than the leptonic one.  The quite slow decreasing of the B/C ratio above 50 GeV/n seems to allow us to exclude the anisotropic CR propagation models and long galactic permanence models, such as Cowsik’s. 72 Nicolò Masi, 13/11/2015, DM State of Art AMS-02 Proton Flux

P.R.L.

Nicolò Masi, 13/11/2015, DM State of Art AMS-02 Helium Flux

P.R.L.

Nicolò Masi, 13/11/2015, DM State of Art AMS-02 Lithium Flux

Nicolò Masi, 13/11/2015, DM State of Art Other anomalies w.r.t the Standard Model

Hadrons

 Change of slope (∆훾~0.1) after 300 GeV/n for protons and Helia (diffusive 훿2 ≠ 훿3 effects, shock model modelization, or nearby high energy sources?)

 Differences in gamma indices (∆훾푝−퐻푒~0.1) between p and He, which seems to remain constant at all energies (source origin)

 Unexpected rise of the pure secondary Lithium spectrum: this could change the orthodoxy!

Nicolò Masi, 13/11/2015, DM State of Art 1. DM must be very massive (several TeV): the “thermal low-mass” and the “naturalness” paradigms must be replaced with a “DM TeV-ish age” one; the DM annihilation cross section should be quite high; 2. The most suitable candidates are SUSY Wino, KK bosons, Little Higgs bosons and Scalars Multiplets, associated to a possible Sommerfeld boson. AMS can detect rises and falls of DM particles up to 3 TeV masses; 3. DM interaction cross sections with SM particles are incredibly tiny for DM masses above 10 GeV. This highlights the not only “dark” but properly “collisionless” behavior of this kind of matter; 4. Recent results from Xenon exclude several types of leptophilic dark matter; 5. AMS-02 showed an excellent capability in doing the described dark matter researches, granting the opportunity to measure CR antiparticle to particle ratios with unprecedented precision; 6. We have to face the astrophysical uncertainties: it will be possible to determine an almost univocal propagation scheme using multiple constraints from nuclei and fundamental particles spectra, removing the background for the dark matter search; 7. For positrons we also have to disentangle DM and pulsars scenarios: the possible flattening of the positron fraction is an intriguing hint of new physics; 8. The behavior of the leptons spectral indices is a new observation and provides important information on the origins and propagation mechanisms of cosmic-ray electrons and positrons; Nicolò Masi, 13/11/2015, DM State of Art 9. The research for an antiproton signal related to heavy DM is going to be published up to 500 GeV: an antiproton anomaly would be very difficult be explained without dark matter;

10. If the antiproton/proton ratio won’t show a decreasing nor an increasing behavior, it will be necessary to study the implications of the flattening;

11. With AMS high precision measurements it is possible to question alternative propagation models which try to explain CR anomalies with pure secondary CRs;

12. Theoretical uncertainties are greater than AMS-02 experimental errors (20÷40% vs few %): a joint effort of the nuclear (spallation cross sections) and astrophysics community (galactic profile and structures) is mandatory to fully exploit the information contained in AMS data;

It seems that nature takes some particular energy scale jumps in the fundamental constituents: we had to wait 66 years between the proton discovery (1917) — a 1 GeV scale particle — and the electroweak bosons one (1983), i.e. 100 GeV scale particles. And other ten and thirty years, respectively, to complete the 100 GeV scale landscape: with the quark top and the Higgs boson. It is not surprising that nature conceals the new particle bestiary over another two order of magnitude barrier, the 10 TeV border, and that these heavy particles may have a suppressed capability to interact with the Standard Model.

Nicolò Masi, 13/11/2015, DM State of Art