Measurement of the Electron and Positron Fluxes with AMS

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Measurement of the Electron and Positron Fluxes

with AMS - 02

Carmen M Gámez López

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★ Charged cosmic rays have mass.

★ They are

absorbed by the 100 km of Earth’s atmosphere (10m The physics of AMS on

the Space Station:

Study of Charged Cosmic Rays

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★ They are

absorbed by the 100 km of Earth’s atmosphere (10m of water)

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★ They are

absorbed by the 100 km of Earth’s atmosphere (10m The physics of AMS on

the Space Station:

★ Located on the

International Space Station

★ In 8 years, over 140

billion charged cosmic rays have been

measured by AMS

★ High precision

measurements of CRs in the GeV-TeV range

★ Anomaly in the electron and positron spectrum.

Dark matter?

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Located on the

measured by AMS

★ High precision

Dark matter?

★ They are

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★ Located on the

measured by AMS

★ High precision

Dark matter?

The physics of AMS on the Space Station:

★ They are

absorbed by the 100 km of Earth’s atmosphere (10m

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Located on the

measured by AMS

★ High precision

Dark matter?

★ They are

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★ Located on the

measured by AMS

★ High precision

Dark matter?

The physics of AMS on the Space Station:

★ They are

absorbed by the 100 km of Earth’s atmosphere (10m

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energy (E ~ p)

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TRD (e/p) Particles are defined by their charge (Z) and

energy (E ~ p)

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Time of Flight (Z, ) energy (E ~ p)

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TRD (e/p)

Silicon Tracker (Z, P)

Particles are defined by their charge (Z) and

energy (E ~ p) Time of Flight (Z, )

Magnet (Z sign)

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energy (E ~ p)

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Time of Flight (Z, )

Magnet (Z sign)

RICH( , Z)

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TRD (e/p)

Particles are defined by their charge (Z) and

energy (E ~ p) Time of Flight (Z, )

Magnet (Z sign)

RICH( , Z) Calorimeter ( )

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energy (E ~ p)

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Time of Flight (Z, )

Magnet (Z sign)

RICH( , Z) Calorimeter ( )

Z, P are measured independently by the Tracker, RICH, TOF and ECAL

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Electron and Positron identification in AMS

TRD

(radiation shape)

ECAL/Tracker (E/p matching)

(shower shape)ECAL e/p identification

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identification in AMS

TRD

(radiation shape)

(shower shape)ECAL

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e/p identification

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Electron and Positron identification in AMS

(shower shape)ECAL TRD

(radiation shape) e/p identification

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identification in AMS

(shower shape)ECAL ECAL/Tracker (E/p matching) TRD

(radiation shape)

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e/p identification

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Electron and Positron identification in AMS

Positron analysis :

Background identification

Charge Confusion

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identification in AMS

Positron analysis :

Background identification

Charge Confusion

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AMS Results Cosmic Ray Positrons

New Astrophysical Sources: Pulsars, …

Supernovae

Positrons from Pulsars

Positrons

from Dark Matter

Protons, Helium, …

Interstellar Medium

Positrons

from Collisions Dark Matter

Electrons

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New Astrophysical Sources: Pulsars, …

Supernovae

Positrons from Pulsars

Positrons

from Dark Matter

Protons, Helium, …

Interstellar Medium

Positrons

from Collisions Dark Matter

Dark Matter Electrons

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Flux of Cosmic Ray Positrons

Low energy positrons mostly come from cosmic ray collisions

M. Aguilar et al. Phys. Rev. Lett. 122 (2019) 041102

AMS 1.9 million positrons Model based on positrons from cosmic ray

collisions.

Astrophysical Journal 729, 106 (2011)

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Low energy positrons mostly come from cosmic ray collisions

AMS 1.9 million positrons Model based on positrons from cosmic ray

collisions.

Astrophysical Journal 729, 106 (2011)

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The positron flux is the sum of

low-energy part from cosmic ray collisions plus a new source at high-energy

AMS Positrons

Source term

Positron from cosmic rays

collisions

AMS Positrons

The cutoff energy Es = 810+310 GeV is established with a confidence of more than 0.9999.

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low-energy part from cosmic ray collisions plus a new source at high-energy

Positron from cosmic rays

collisions

Source term

Energy (GeV)

The cutoff energy Es = 810+310 GeV is established with a confidence of more than 0.9999.

AMS Positrons

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Flux of Cosmic Ray Electrons

The contribution from cosmic ray collisions is negligible

AMS 28.1 million electrons

Electrons from cosmic ray collisions

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The contribution from cosmic ray collisions is negligible

AMS 28.1 million electrons

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The Origin of Cosmic Ray Electrons

The electron flux can be described by two power law functions a and b

Electrons from cosmic ray collisions AMS electrons

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The electron flux can be described by two power law functions a and b

AMS electrons

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Physics of Cosmic Electrons to 2024

AMS data 2018

Projection to 2024 based on data trend

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AMS data 2018

Projection to 2024 based on data trend

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The Origin of Cosmic Ray Positrons

★ Pulsars produce and accelerate positrons to high energies.

★ Pulsars may induce an anisotropy in the arrival direction of the

particles

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The Origin of Cosmic Ray Positrons

_★ Pulsars may induce an anisotropy in the arrival direction of the

particles

rRotation axis

Light rays

Magnetic field lines

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The origin of Cosmic Rays Positrons

Antiproton data show a similar trend as positrons

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Antiproton data show a similar trend as positrons

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Cosmic Rays Collisions

Data 2018

Dark Matter Model

The Origin of Cosmic Ray Positrons

Dark Matter Model Prediction of Positron Spectrum with a characteristic sharp drop-off at high energies

Data 2018

Dark Matter Model (Mass=1.2 TeV)

J. Kopp, Phys. Rev. D 88, 076013 (2013)

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Data 2018

Dark Matter Model (Mass = 1.2 TeV)

Dark Matter Model Prediction of Positron Spectrum with a characteristic sharp drop-off at high energies

39 J. Kopp, Phys. Rev. D 88, 076013 (2013)

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Dark Matter Model (Mass = 1.2 TeV) + cosmic rays collisions

Projection to 2024 based on dark matter model

Positrons and Dark Matter Model by 2024

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Dark Matter Model (Mass = 1.2 TeV) + cosmic rays collisions

Projection to 2024 based on dark matter model

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AMS Positron cosmic ray anisotropy

Analysis of the arrival directions of the positrons

The anisotropy in galactic coordinates

★ The positron flux is found to be consistent with isotropy

Positrons Isotropic map

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Analysis of the arrival directions of the positrons

The anisotropy in galactic coordinates

★ The positron flux is found to be consistent with isotropy

PPositrons PIsotropic map

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Conclusions

★ The CR positron flux shows that, at high energy, its origin cannot be purely secondary. Thus, the inclusion of primary sources is required; typically, classified in two scenarios

Astrophysical

source Dark matter

annihilation

★ The measurement made by AMS of the CR electron flux cannot be described by a single power law. The observations required a two power laws description, with a primary source term.

★ The source term observed in the positron and electron fluxes is a clear evidence that they have a different origin

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