Search for Dark Matter The AMS-02 Experiment

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Search for Dark MatterThe AMS-02 Experiment

• Ignacio Sevilla Noarbe
• (CIEMAT, Madrid)
• on behalf of the AMS collaboration

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Outline

• The AMS experiment on the ISS.
• Dark matter and indirect search.
• Prospects for the AMS experiment.

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The AMS experiment

• AMS (Alpha Magnetic Spectrometer) is a particle
  physics experiment in space.
• It will detect and identify huge statistics of
  primary and secondary cosmic rays, up to Z26, in
  the GeV-TeV range.
• Among its physics goals, are anti-matter and
  dark matter search, cosmic ray propagation
  studies.
• It is being mainly built in Europe, in close
  collaboration with NASA, involving hundreds of
  scientists and engineers and many institutions
  worldwide.
• AMS-01 was tested successfully on shuttle flight
  STS91 for ten days in 1998. AMS-02 will be on the
  ISS for three years from early 2008.

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The AMS experiment

• Superconducting magnet (BL2 0.85 Tm2)

• Silicon Tracker (rigidity, charge)

• Scintillator system (TOF) (ß, dE/dx, trigger)

• Transition Radiation Detector (e/p)

• Ring Imaging Cherenkov (ß, charge)

2 m 7 Tons

• Electromagnetic Calorimeter(energy, e/p)

• Anticoincidence counters, star-tracker, GPS

• Also gamma rays in conversion or ECAL

2 m
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Dark matter neutralinos

• The case for non-baryonic dark matter is well
  established by several independent measurements
  and theoretical approaches.

?Mh2 0.135 0.008 ?bh2 0.0224 0.0009

• From the observational point of view of AMS, one
  of the best candidates for detection is the
  neutralino, which presents other interesting
  qualities
• Supersymmetry predicts the existence of these
  particles without an a priori requirement for a
  WIMP dark matter candidate.
• Neutral, weak-interacting and stable in R-parity
  conserving SUSY models where the LSP is a
  neutralino.
• Current most accepted structure formation (?CDM)
  theory require weakly-interacting massive
  particles (WIMPs).
• HOWEVER
• Neutralinos (or supersymmetry for that case)
  have not been observed yet.

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Dark matter detection

• WIMP DM component detection
• Direct detection via inelastic scattering (DAMA,
  CDMS, UKDMC).
• Indirect detection
• Annihilation in Earth/Sun ? ?? ? (ANTARES,
  ICECUBE)
• Annihilation in galactic halo ?
• ANOMALIES IN CR SPECTRA
• These can be studied from balloon (BESS, CAPRICE)
  and space-borne experiments (PAMELA, GLAST).
• AMS on the International Space Station will
  provide enough statistics to perform a
  multi-channel approach.

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Indirect searches with AMSdetection channels
Possible detectable products from ???xx with
small physical backgrounds

• Gamma rays
• They are originated either from annihilation into
  a final state containing Z? or ?? (line signal)
  or from the decay of other primary annihilation
  products (continuum signal).
• Positrons
• Primarily from the decay of gauge bosons
  (e.g.,WW-) as primary annihilation products or
  from heavy quark/lepton decay
• Antiprotons and antideuterons
• Production in WIMP annihilations by hadronization
  of quark and gluon subproducts.

? ray telescopes and satellites
AMS
Balloons
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Indirect searches with AMSCR flux and energy
ranges
Particle Energy range p 0.1 up to
several TeV p- 0.5-300 GeV e-
0.1 up to O(TeV) e 0.1-300
GeV He 1 up to several TeV anti
HeC 1 up to O(TeV) Light Isotopes 1-10
GeV/nucleon g 1-1000 GeV
1 p per second above 100 GeV 105 C after 3 years
above 100 GeV 105 10Be after 3 years above 100 GeV
Approximate rates (horizontal lines) indicate
number of particles inside geometrical acceptance
integrated from the energy where the spectrum
crosses the line. We assume 0.45 m2sr and
spectral index 2.8
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Indirect searches with AMSexpected performances

• Positrons
• TRD selection up to 300 GeV ECAL e/p selection
  with shower shape
• Overall Proton rejection of 105
• Acceptance 4.510-2 m2sr

• Antiprotons
• Charge confusion control for p TOF ß, TRD, ECAL
  for e-
• Proton rejection of 106 e - 104
• Acceptance 310-2 m2sr up to 20 GeV

• Gamma rays ECAL(TRK)
• Angular resolution under 3º(0.1º) over 10 GeV.
• Energy resolution 5 over 10 GeV
• Acceptance ECAL(TRK) 5(3)10-2 m2sr from 10
  GeV.
• Proton rejection 105 e - 104

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Indirect searches with AMSexpected performances

• Positrons
• TRD selection up to 300 GeV ECAL e/p selection
  with shower shape
• Overall Proton rejection of 105
• Acceptance 4.510-2 m2sr

• Antiprotons
• Charge confusion control for p TOF ß, TRD, ECAL
  for e-
• Proton rejection of 106 e - 104
• Acceptance 310-2 m2sr up to 20 GeV

• Gamma rays ECAL(TRK)
• Angular resolution under 3º(0.1º) over 10 GeV.
• Energy resolution 5 over 10 GeV
• Acceptance ECAL(TRK) 5(3)10-2 m2sr from 10
  GeV.
• Proton rejection 105 e - 104

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Indirect searches with AMSexpected performances

• Positrons
• TRD selection up to 300 GeV ECAL e/p selection
  with shower shape
• Overall Proton rejection of 105
• Acceptance 4.510-2 m2sr

• Antiprotons
• Charge confusion control for p TOF ß, TRD, ECAL
  for e-
• Proton rejection of 106 e - 104
• Acceptance 310-2 m2sr up to 20 GeV

• Gamma rays ECAL(TRK)
• Angular resolution under 3º(0.1º) over 10 GeV.
• Energy resolution 5 over 10 GeV
• Acceptance ECAL(TRK) 5(3)10-2 m2sr from 10
  GeV.
• Proton rejection 105 e - 104

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Indirect searches with AMSflux estimations
f (m-2 s-1 sr-1 GeV-1) fbg fsignal
Local Background Flux determined by propagation
of CR yield per unit volume through simulation
(GALPROP)
Gas (HI,H2,HII) distribution
CR source distribution and spectrum (index,
abundances)
Diffusion model (reacceleration, diffusion) and
parameters (D,size h, cross-sections)

• Physical background
• Antimatter channels
• secondary products from cosmic ray spallation in
  the interstellar medium
• Gamma ray channel
• diffuse Galactic emission from cosmic ray
  interaction with gas (p0 production, inverse
• Compton, bremsstrahlung)

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Indirect searches with AMSflux estimations
f (m-2 s-1 sr-1 GeV-1) fbg fsignal
Local Flux determined by propagation of CR yield
per unit volume through simulation (GALPROP)
(propagation model and parameters )
CR yield per unit volume (r,z,E)
gann(E).ltsvgt(??(r,z) /m?)2
gann(E) particle production rate per
annihilation
COSMOLOGY
ASTROPHYSICS
WMAP () constraints on ??h2
Rotational velocity measurements
m? neutralino mass
DM density profile shape ( boost factors)
HEP
ltsvgt coannihilation cross-section
Accelerator constraints
??(r,z) density distribution
SUSY parameter space (5)
Boost factors clumpiness, cuspiness, baryon
interaction, massive central black hole
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Indirect searches with AMSpositron channel

• Positrons
• The relative fluxes of electrons and positrons
  are very uncertain at energies above 10 GeV.
• An excess of positron fraction is claimed by the
  HEAT balloon experiment, maybe hinting to
  neutralinos?
• Discovery potential sensible to local DM
  distribution.
• High sensitivity to local clumpiness.

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Indirect searches with AMSpositron channel
m? 98 GeV M0 60 m1/2 250 tan ß 10 A0
0 ltsvgt 10-27
Credit Jonathan Pochon - LAPP

• Positrons
• Sensitivity to B (bulk) and E (focus point)
  benchmark mSUGRA models (Battaglia et al.
  hep-ph/0306219).
• For these and other benchmark scenarios, boost
  factors needed to fit HEAT data range from 103 to
  105.

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Indirect searches with AMSpositron channel
m? 124 GeV m0 1530 m1/2 300 tan ß 10
A0 0 ltsvgt 10-29
Credit Jonathan Pochon - LAPP

• Positrons
• Sensitivity to B (bulk) and E (focus point)
  benchmark mSUGRA models (Battaglia et al.
  hep-ph/0306219).
• For these and other benchmark scenarios, boost
  factors needed to fit HEAT data range from 103 to
  105.

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Indirect searches with AMSpositron channel
m? 208 GeV m0 500 m1/2 500 tan ß 50
A0 500 ltsvgt 10-26
Credit Jonathan Pochon - LAPP

• Positrons
• Sensitivity to HEAT, p-, EGRET-data fitted model
  (de Boer et al. hep-ph/0309029).
• In this case, ???bbbar favored (no sharp cutoff).
• Boost factor needed to fit HEAT data 102

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Indirect searches with AMSpositron channel
Credit Jonathan Pochon - LAPP

• Positrons
• More general mSUGRA scan minimal boost factors
  for discovery.
• Boost factor needed quite sensitive to
  assumptions at GUT scale.

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Indirect searches with AMSpositron channel

• Positrons
• Alternative scenario the lightest Kaluza-Klein
  particle in the Universal Extra Dimensions model
  (a 300 GeV KK photon in this case).
• Boost factor needed 1700 to fit HEAT data, 60
  for discovery.

Credit Jonathan Pochon - LAPP
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Indirect searches with AMSantiproton channel

• Antiprotons
• They seem to follow expected spectrum from CR
  interaction with ISM up to 10 GeV.
• However there are large uncertainties above 10
  GeV and below 1 GeV (though now disfavored in
  this region).

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Indirect searches with AMSantiproton channel
Antiprotons

• Sensitivity to wide range of cases
• Very favorable flat spectrum (Ullio
  astro-ph/9904086) (high mass 1.4 TeV high boost
  factor 7103).

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Indirect searches with AMSantiproton channel
Antiprotons

• Sensitivity to wide range of cases
• De Boer et al. (hep-ph/0309029) data-fitted model
  would be detectable (boost factor required of
  6.5).

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Indirect searches with AMSantiproton channel
Antiprotons

• Sensitivity to wide range of cases
• Conservative (no boost factor)
  detection/exclusion of AMSB scenarios (Profumo et
  al. hep-ph/0406018).

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Indirect searches with AMSantiproton channel
Antiprotons

• Background calculations can be very much
  improved with B/C and other isotopic ratio
  measurements.

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Indirect searches with AMSgamma channel
B
B

• Gamma rays
• Many experiments will be covering the little
  known 1-300 GeV range in the next decade.
• Case considered Galactic center treated as point
  source. Favorable conditions to detect or exclude
  AMSB scenarios benchmark points of parameter
  space accesible in case of cuspy profile as well
  as several KK candidates.

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Summing up

• Recent research points to a non-baryonic
  component of dark matter. Neutralinos are one of
  the best candidates to date.
• AMS will be a multipurpose detector in space that
  will look for signatures of neutralino
  coannihilation in the galactic halo, making use
  of high statistics, particle identification and
  multichannel capabilities
• B/C and Be ratios will impose severe constraints
  to galaxy models and diffusion parameters for
  background estimation.
• Positrons signal at gt10 GeV will be confirmed or
  disproved.
• Antiprotons the spectrum at gt50 GeV will be
  measured with great sensitivity.
• Gammas (from Galactic Center) visible signal in
  cuspy profile scenarios or other boost factors.
• A single experiment that will enable a
  simultaneous study of several cases of the MSSM
  parameter space as well as other scenarios such
  as KK-particles and AMSB neutralinos.

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Backup
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The AMS experiment the superconducting magnet

• Its purpose is to bend the trajectories of
  charged particles.
• It will be the first superconducting magnet to
  operate in space.
• It is a system of 12 racetrack coils 2 dipole
  coils cooled to 1.85 K by 2.5 m3 of superfluid
  helium.
• BL2 0.86 Tm2

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The AMS experiment the Silicon Tracker

• It will measure the rigidity (momentum/charge)
  and charge.
• With over 6 m2 of active surface, it will be the
  largest ever built before the LHC.
• Based on 8 thin layers of double-sided silicon
  microstrips, a spatial resolution of 10 mm will
  be achieved.
• This means around 200k channels.

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The AMS experiment the Time Of Flight system

• This sub-detector will measure the velocity of
  the particle by recording time of passage and
  position in 4 different planes.
• Each plane has 8-10 scintillator paddles seen by
  2 PMTs on each side.
• It can measure velocities with 3.6 relative
  error (for ? 1 protons).

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The AMS experiment theTransition Radiation
Detector

• The TRD is based on the radiation emitted by a
  moving charged particle when it traverses two
  different media.
• It will perform hadron/lepton separation.
• There are 20 layers of foam separated by drift
  tubes.
• h/e rejection of 102 103 in the range 3 300
  GeV.

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The AMS experiment the RICH detector

• Makes use of the Cherenkov light emitted in the
  radiator by relativistic charged particles.
• We can obtain the velocity and absolute charge of
  incoming particles.
• 3 cm thick aerogel radiator 680 multianode
  photomultipliers.
• We can achieve velocity measurements with a 0.1
  relative error for protons.
• CIEMAT is a major partner in this effort.

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The AMS experiment the Electromagnetic
Calorimeter

• The ECAL registers electromagnetic showers
  initiated by the particles.
• Thus we can measure the energy of the primary.
• It consists of 9 superlayers of scintillator/lead
  connected to 324 multianode photomultipliers.
• Energy is measured with a 3 error at 100 GeV.

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Gamma ray in a 3-prong e- event from test beam
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From D.Hooper and J.Silk (astro-ph/0409104)

• Sensitivity to bino-like LSP neutralinos up to
  310-27 for masses 100 GeV.
• Sensitivity to LSP neutralinos in AMSB scenarios
  up to several hundred GeV (even a few TeV).
• Sensitivity to annihilations of KK excitations of
  SM fields up to 1 TeV.

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Dark matter problem observations
OMEGA
SCALE
?m ? 0.1
Galactic
Cluster
?m ? 0.2-0.3
Cosmological
?0 ? 1
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Dark matter problemtheoretical arguments

• CMB characteristics are better explained in
  inflationary models. (Most of) these in turn
  predict ? 1.

• If ?lum ?mass it turns out that structure
  should have formed rapidly requiring unobserved
  high fluctuations in the CMB.

• If ? ? 1, as we know that ?0 1 now, at Planck
  time it should have been 1?10-60 (? varies
  quickly if not unity).

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Dark matter problem candidates

• The case for non-baryonic DM
• limited by well-tested BBN Deuterium and He-3
  observations.
• observations from MACHO experiments cannot
  account for all galactic dark matter.
• CMB acoustic peaks power spectrum of universal
  inhomogeneity cluster baryon fraction implies
• One of the best descriptions to date for
  structure formation ?CDM scenario requires
  WIMPs (or axions).
• Candidates neutrinos, SUSY particles, axions,
  Kaluza-Klein particles, many others

?Mh2 0.14 0.02 ?bh2 0.024 0.001
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