the lc and the cosmos: connections in supersymmetry jonathan feng uc irvine american linear collider...
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![Page 1: The LC and the Cosmos: Connections in Supersymmetry Jonathan Feng UC Irvine American Linear Collider Physics Group Seminar 20 February 2003](https://reader030.vdocuments.us/reader030/viewer/2022032800/56649d4c5503460f94a2a342/html5/thumbnails/1.jpg)
The LC and the Cosmos:Connections in Supersymmetry
Jonathan Feng
UC Irvine
American Linear Collider Physics Group Seminar
20 February 2003
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February 2003 ALCPG Seminar Feng 2
The Particle/Cosmo Interface
Many Grand Questions:• Baryogenesis
– Why is there more matter than anti-matter?
• Ultra-high Energy Cosmic Rays – What are the highest energy particles detected?
…• Dark Matter
– What is most of the matter in the universe made of?
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February 2003 ALCPG Seminar Feng 3
Dark Matter
• The dawn of precision cosmology:
t0 = 13.7 0.2 Gyr
total = 1.02 0.02
DM = 0.23 0.04
baryon = 0.044 0.004< 0.015 (m < 0.23 eV for degenerate case)
WMAP (2003)
• We live in interesting times:– We know how much dark matter there is – We have no idea what it is
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February 2003 ALCPG Seminar Feng 4
WIMPs
• Weakly-interacting particles with weak-scale masses naturally provide DM
• Either– a devious coincidence,
or – a strong, fundamental,
and completely independent motivation for new physics at the electroweak scale
Jungman, Kamionkowski, Griest (1995)
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February 2003 ALCPG Seminar Feng 5
Limitations of Separate Approaches
• Dark matter experiments cannot discover SUSY– can only provide rough constraints on
mass, interaction strengths
• Colliders cannot discover dark matter– can only verify > 10-7 s, 24 orders of
magnitude short of the age of the universe
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February 2003 ALCPG Seminar Feng 6
Synergy
Collider Inputs
SUSY Parameters
Annihilation N Interaction
Relic Density Indirect Detection Direct Detection
Astrophysical and Cosmological Inputs
Feng, Nojiri (2002)
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February 2003 ALCPG Seminar Feng 7
Annihilation
• Neutralino annihilation: sensitive to most SUSY parameters
• Top diagram vanishes for heavy scalar superpartners
• Bottom diagram vanishes for = pure Bino
requires– Light scalars, or– Mixed neutralinos,
light Higgsinos
typically, rich LC physics
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February 2003 ALCPG Seminar Feng 8
Relic Density• Extreme sensitivity to
neutralino mixing
Feng, Matchev, Wilczek (2000)
Relic density regions and gaugino-ness (%)
• Extreme sensitivity to degeneracies
E.g., – co-annihilation requires mass measurements much better than
m ~ T ~ m/25
Accurate determination requires full capabilities of the Linear Collider
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February 2003 ALCPG Seminar Feng 9
• Many handles at colliders. E.g., gaugino-ness measurements:
– LHC/LC: Mass measurements of all charginos and neutralinos
– LC: Polarized measurements of lighter chargino pair production
LC500 Right-polarized chargino pair production cross sections (fb)
Feng, Murayama, Peskin, Tata (1995)
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February 2003 ALCPG Seminar Feng 10
Dark Matter Detection
• Direct detection depends on N scattering
• Indirect detection depends on annihilation
in galactic center e+ in halo
or both
in centers of the Sun and Earth
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February 2003 ALCPG Seminar Feng 11
Indirect Detection Experiments
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February 2003 ALCPG Seminar Feng 12
Dark Matter Detection
Particle probes Direct DM detection Indirect DM detection
• Astrophysical and particle searches are complementary
• SUSY at LC500 dark matter signal before ~2007 (in mSUGRA)
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February 2003 ALCPG Seminar Feng 13
Particle/Cosmo Interface
• Particle Physics + standard cosmology predictions for
Direct detection ratesIndirect detection rates
• If consistent with observations and experiments, we understand the universe back to 10-8 sec (T ~ 10 GeV)
[Cf. Big Bang nucleosynthesis at 1 sec (T ~ 1 MeV) ]
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February 2003 ALCPG Seminar Feng 14
What if there are discrepancies?
• Thermal relic density need not be the actual relic density – late decays, … – The mismatch tells us about the history of the
universe between 10-8 s < t < 1 s
• The detection rate need not be the actual detection rate– the mismatch tells us about halo profiles, dark
matter velocity distributions,…
• LHC/LC will not only identify DM as SUSY, but also may shed light on “astrophysical” problems
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February 2003 ALCPG Seminar Feng 15
Example: Halo profile at the galactic center
• Halo profiles are currently not well-known (cuspy, clumpy, …)
• An indirect dark matter signal is photons from the galactic center:
ParticlePhysics
Astro-Physics
Feng, Matchev, Wilczek (2000)Buckley et al. (1999)
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February 2003 ALCPG Seminar Feng 16
superWIMPs
• WIMP motivations are strong, suggest optimism for detection:weaker interactions too much relic density
• But this relation may be broken:
E.g., gravitino LSP, WIMP NLSP– WIMP freezes out as usual,
but then decays to gravitino– gravitino inherits the desired – Gravitino interacts only
gravitationally, is a superWIMP
Feng, Rajaraman, Takayama (2003)
Bino for mgravitino = 0.1, 0.3, 1, 3 TeV from below
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February 2003 ALCPG Seminar Feng 17
Implications• Gravitino dark matter escapes all dark matter
experiments
• Astrophysical superWIMP detection depends on NLSP:
superWIMP– diffuse signature– CMB deviations from black-body
superWIMP– CMB anisotropy
e superWIMPs, q superWIMPs, …
• Colliders may see meta-stable massive charged particles, provide valuable information
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February 2003 ALCPG Seminar Feng 18
Conclusions
• Dark matter and EWSB are independent motivations for new physics; both point to the weak scale
• Both collider and astrophyical/cosmological data are required to get anywhere
• High sensitivity to SUSY parameters – LC inputs are likely to be extremely valuable