wimps and superwimps jonathan feng uc irvine mit particle theory seminar 17 march 2003

WIMPs and superWIMPs

Jonathan Feng

UC Irvine

MIT Particle Theory Seminar

17 March 2003

17 March 2003 MIT Feng 2

Dark Matter• The dawn (mid-morning?) of precision cosmology:

DM = 0.23 0.04

total = 1.02 0.02

baryon = 0.044 0.004

t0 = 13.7 0.2 GyrWMAP (2003)

• We live in interesting times:We know how much dark matter there is We have no idea what it is

• Our best evidence for new particle physics


WIMPs• Weakly-interacting particles with

weak-scale masses decouple with DM ~ 0.1; this is remarkable

[Cf. quarks with natural B ~10-11 ]

• Either– a devious coincidence,

or – a strong, fundamental, and

completely cosmological motivation for new physics at the electroweak scale

Jungman, Kamionkowski, Griest (1995)


Outline

• Explore new possibilities for particle dark matter

• Guiding principles:

– Must be well-motivated from particle physics viewpoint

– Must naturally produce desired DM (this is all we know!)

WIM

Ps

supe

rWIM

Ps

SUSY Extra D

FRT*

CFM*

*Cheng, Feng, Matchev (2002)*Feng, Rajaraman, Takayama (2003)


SUSY WIMPs

Feng, Matchev, Wilczek (2000)

Relic density regions and gaugino-ness (%)

• Neutralinos:• fermionic partners of

, Z, W0, h0

• DM ~ 0.1 in much of parameter space

• Requirements:• high supersymmetry

breaking scale (supergravity)

• R-parity conservation


SUSY WIMP Detection

Particle probesDirect DM detectionIndirect DM detection

• Astrophysical and particle searches are promising: many possible DM signals before 2007

• This is generally true of WIMPs: undetectable weak interactions weak annihilation too much relic density


Extra D WIMPs

• Kaluza (1921) and Klein (1926) considered D=5, with 5th dimension compactified on circle S1 of radius R:

D=5 gravity D=4 gravity + EM + scalar

GMN G + G5 + G55

• Kaluza: “virtually unsurpassed formal unity...which could not amount to the mere alluring play of a capricious accident.”


• Problem: gravity is weak

• Solution: introduce extra 5D fields: GMN , VM , etc.

• New problem: many extra 4D fields; some with mass n/R, but some are massless! E.g., 5D gauge field:

• New solution…

good

bad


• Compactify on S1/Z2 instead (orbifold); require

• Unwanted scalar is projected out:

• Similar projection on fermions chiral 4D theory, …

• Very simple (requires UV completion at R)Appelquist, Cheng, Dobrescu (2001)

good

bad


KK-Parity• An immediate consequence: conserved KK-parity KK

Interactions require an even number of odd KK modes

• 1st KK modes must be pair-produced at colliders

• weak bounds: R > 200 GeV

• LKP (lightest KK particle) is stable – dark matter!

Appelquist, Yee (2002)

Macesanu, McMullen, Nandi (2002)


Other Extra D Models

• SM on brane; gravity in bulk (brane world)– Requires localization mechanism– No concrete dark matter candidate

• fermions on brane; bosons and gravity in bulk– Requires localization mechanism– R > few TeV from f f V

1 f f– No concrete dark matter candidate

• everything in bulk (Universal Extra D)– No localization mechanism required– Natural dark matter candidate – LKP

_ _


UED and SUSYSimilarities:• Superpartners KK partners• R-parity KK-parity• LSP LKP• Bino dark matter B1 dark matter

Sneutrino dark matter 1 dark matter...

Not surprising: SUSY is also an extra (fermionic) dimension theory

Differences:• KK modes highly degenerate, split by EWSB and

loops• Fermions Bosons


Minimal UED KK Spectrum

Cheng, Matchev, Schmaltz (2002)

loop-levelR = 500 GeV

tree-levelR = 500 GeV


Extra D WIMPs

• LKP is nearly pure B1 in minimal model (more generally, a B1-W1 mixture)

• Relic density:Annihilation through

Preferred mass range ~ 1 TeV, variations from co-annihilations Servant, Tait (2002)


Co-annihilation

• But degeneracy co-annihilations important

• Co-annihilation processes:

• Preferred mB1: l1 lowers it, q1 raises it; 100s of GeV to few TeV possible

Dot: 3 generationsDash: 1 generation1% degeneracy5% degeneracy

Servant, Tait (2002)


• s-channel enhanced by

B1-q1 degeneracy

• Constructive interference: lower bounds on scalar , spin

B1 Dark Matter Detection

Direct Detection

Cheng, Feng, Matchev (2002)

t-channelh exchange

s- and u-channelB1q q1 B1q

scalar spin


B1 Dark Matter Detection

• Indirect Detection: – Positrons from the galactic halo– Muons from neutrinos from the Sun and Earth– Gamma rays from the galactic center

• All rely on annihilation, very different from SUSY– For neutralinos (Majorana fermions), f f is

chirality suppressed– B1B1 f f isn’t; generically true for bosons


Positrons


• Here fi(E0) ~ (E0mB1), and thepeak is not erased by propagation(cf. W+Wee)

• AMS will have e/e separation at 1 TeV and see ~1000 e above 500 GeV

Moskalenko, Strong (1999)


Muons from Neutrinos

Cheng, Feng, Matchev (2002)Hooper, Kribs (2002)

Bertone, Servant, Sigl (2002)

• Muon flux is

• B1B1 is also unsuppressed, gives hard neutrinos, enhanced flux

Ritz, Seckel (1988)Jungman, Kamionkowski, Griest (1995)

Discovery reach

dege

nera

cy


Gamma Rays


• B1B1 is loop-suppressed, but light quark fragmentation gives hardest photons, so absence of chirality suppression helps again

• Results sensitive to halo clumpiness; choose moderate value

Bergstrom, Ullio, Buckley (1998)

Integrated photon flux ( J = 500)_


What about KK gravitons?

• G1 may be the LKP. In fact, loop contributions, typically positive, are negligible for G1.

• For that matter, what about gravitinos in SUSY? In supergravity,

m3/2 ~ m0 ~ M1/2 ~ <F>/MPl,

unknown O(1) coefficients determine ordering. The gravitino may be the LSP.

• These possibilities are very similar; consider in parallel.


superWIMPs

• Suppose LKP is G1. If NLKP is B1, B1 freezes out with the usual desired , then decays much later via B1 G1

• G1 inherits the desired retains all WIMP virtues

• BUT: G1 is superweakly-interacting, and so undetectable by all dark matter searches

• Only possible signal is in WIMP superWIMP decays

Feng, Rajaraman, Takayama (2003)

gravitino graviton

msWIMP = 0.1, 0.3, 1 TeV (from below)


BBNExcluded Regions (shaded)

• Late decays may destroy BBN light element abundance predictions

• typically quickly thermalize, BBN constrains total energy release X = nSWIMP / nBG

• Constraints weak for early decays: universe is hot,

BG e+e suppresses spectrum at energies above nuclear thresholds

Cyburt, Ellis, Fields, Olive (2002)


CMB

gravitino graviton

mSWIMP as indicated

Excluded regions (above CMB contours)

• Late decays may also destroy black-body spectrum of CMB

• Again get weak constraints for early decays, when e e

e X eX e e

are all effective

• superWIMP DM:

• mWIMP, mSWIMP ,

• SWIMP = DM abundance YSWIMP

Feng, Rajaraman, Takayama (2003)


superWIMP Dark Matter

gravitino graviton

Weak-scale superWIMPs are viable cold dark matter

Feng, R

ajaraman, T

akayama (2003)


Is it testable?

• BBN versus CMB baryometry is a powerful probe

Cyburt, Fields, Olive (2003)Fields, Sarkar, PDG (2002)

WMAP

D = CMB

but

7Li is low


7Li low

4He low

D low

D high

105 s

3 105 s

106 s

3 106 s

107 s

X and

10-8 GeV

3 10-9 GeV

10-9 GeV

3 10-10 GeV

10-10 GeV

Feng, Rajaraman, Takayama (2003)Cyburt, Ellis, Fields, Olive (2002)


Conclusions

• Guiding principles:– well-motivated particle physics– naturally correct DM

• WIMPs from Extra Dimensions– B1: qualitatively new signals– Many other candidates to investigate

• superWIMPs: gravitinos/gravitons naturally yield desired thermal relic density, but are inaccessible to all conventional searches– Bino NLSP: BBN, CMB signals– Many other NLSP candidates to investigate

• Escape from the tyranny of neutralino dark matter!W

IMP

ssu

perW

IMP

s

SUSY Extra D

wimps and superwimps jonathan feng uc irvine mit particle theory seminar 17 march 2003

Documents

gravity d

stable dark matter

kk interactions

kk modes

d theory

d fields

extra d modelssm

gevlkp lightest kk particle