WIMPs and super WIMPs from Extra Dimensions Jonathan

WIMPs and super. WIMPs from Extra Dimensions Jonathan Feng UC Irvine Johns Hopkins Theory Seminar 31 January 2003 Johns Hopkins

Dark Matter • Our best evidence for new particle physics • We live in interesting times – we know how much there is (WDM = 0. 25 +/- 0. 04) – but not what it is (non-baryonic, cold) • WIMPs are attractive – predicted in many particle theories (EWSB) – naturally give thermal relic density WDM ~ O(1) – WDM < 1 cc f f not small c f not small, so testable: promising for direct, indirect detection 31 January 2003 Johns Hopkins 2

Candidates from Particle Physics • Supersymmetry – Neutralinos – partners of g, Z, W, h – Requirements: high supersymmetry-breaking scale (supergravity) R-parity conservation • Extra Dimensions – Kaluza-Klein particles – partners of g, Z, W, h, Gmn, … – Requirements: universal extra dimensions Cheng, Feng, Matchev (2002) Feng, Rajaraman, Takayama 31 January 2003 Johns Hopkins 3

Universal Extra Dimensions • Kaluza (1921) and Klein (1926) considered D=5, with 5 th dimension compactified on circle S 1 of radius R: D=5 gravity D=4 gravity + EM + scalar GMN Gmn + Gm 5 + G 55 • Kaluza: “virtually unsurpassed formal unity. . . which could not amount to the mere alluring play of a capricious accident. ” 31 January 2003 Johns Hopkins 4

• Problem: gravity is weak • Solution: introduce extra 5 D fields: GMN , VM , etc. • New problem: many extra 4 D fields; some with mass n/R, but some are massless! E. g. , 5 D gauge field: good bad • A new solution… 31 January 2003 Johns Hopkins 5

• Compactify on S 1/Z 2 instead (orbifold); require • Unwanted scalar is projected out: good bad • Similar projection on fermions 4 D chiral theory, … • Very simple (requires UV completion at L >> R-1 ) Appelquist, Cheng, Dobrescu (2001) 31 January 2003 Johns Hopkins 6

KK-Parity • An immediate consequence: conserved KK-parity (-1)KK Interactions require an even number of odd KK modes • 1 st KK modes must be pair-produced at colliders Macesanu, Mc. Mullen, Nandi (2002) • weak bounds: R-1 > 200 Ge. V Appelquist, Yee (2002) • LKP (lightest KK particle) is stable – dark matter Kolb, Slansky (1984) Saito (1987) 31 January 2003 Johns Hopkins 7

Other Extra Dimension 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-1 > few Te. V from f f Vm 1 f f – No concrete dark matter candidate • everything in bulk (UED) – No localization mechanism required – Natural dark matter candidate – LKP 31 January 2003 Johns Hopkins 8

UED and SUSY Similarities: • Superpartners KK partners • R-parity KK-parity • LSP LKP • Bino dark matter B 1 dark matter Sneutrino dark matter n 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 31 January 2003 Johns Hopkins 9

Minimal UED KK Spectrum tree-level R-1 = 500 Ge. V loop-level R-1 = 500 Ge. V Cheng, Matchev, Schmaltz (2002) 31 January 2003 Johns Hopkins 10

1 B WIMP Dark Matter • LKP is nearly pure B 1 in minimal model (more generally, a B 1 -W 1 mixture) • Relic density: Annihilation through Servant, Tait (2002) 31 January 2003 Johns Hopkins 11

Co-annihilation • But degeneracy coannihilations important • Co-annihilation processes: Dot: 3 generations Dash: 1 generation 1% degeneracy 5% degeneracy • Preferred m. B 1: l 1 lowers it, q 1 raises it; 100 s of Ge. V to few Te. V possible Servant, Tait (2002) 31 January 2003 Johns Hopkins 12

1 B Dark Matter Detection Direct Detection t-channel h exchange s- and u-channel B 1 q q 1 B 1 q sscalar sspin • s-channel enhanced by B 1 -q 1 degeneracy Cheng, Feng, Matchev (2002) • Constructive interference: lower bound on both sscalar and sspin 31 January 2003 Johns Hopkins 13

1 B 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), cc f f is chirality suppressed – B 1 B 1 f f isn’t; generically true for bosons 31 January 2003 Johns Hopkins 14

Positrons Moskalenko, Strong (1999) • Here fi(E 0) ~ d(E 0 -m. B 1), and the peak is not erased by propagation (cf. cc W+W- e+n e-n) • AMS will have e+/e- separation at 1 Te. V and see ~1000 e+ above 500 Ge. V 31 January 2003 Johns Hopkins Cheng, Feng, Matchev (2002) 15

Muons from Neutrinos • Muon flux is • B 1 B 1 n n is also unsuppressed, gives hard neutrinos, enhanced m flux Cheng, Feng, Matchev (2002) Hooper, Kribs (2002) Bertone, Servant, Sigl (2002) 31 January 2003 Johns Hopkins degeneracy Ritz, Seckel (1988) Jungman, Kamionkowski, Griest (1995) Discovery reach 16

Gamma Rays g g is loopsuppressed, but light quark fragmentation gives hardest photons, so absence of chirality suppression helps again • Results sensitive to halo clumpiness; choose moderate value • B 1 B 1 Bergstrom, Ullio, Buckley (1998) 31 January 2003 Johns Hopkins _ Integrated photon flux ( J = 500) Cheng, Feng, Matchev (2002) 17

super. WIMPs Feng, Rajaraman, Takayama • What about the KK graviton? LKP may be 1 st KK graviton G 1 • If NLKP is B 1, B 1 freezes out, then decays much later via B 1 g G 1 • G 1 is a super. WIMP: retains all WIMP virtues, but is undetectable by conventional dark matter searches (Gravitino is another possible super. WIMP) 31 January 2003 gravitino graviton ms. WIMP = 0. 1, 0. 3, 1, 3 Te. V (from below) Johns Hopkins 18

BBN and CMB • Late decays may destroy BBN successes or distort CMB ms. WIMPYs. WIMP (Ge. V) • Both constraints may be satisfied • Possible signals in diffuse photon flux gravitino graviton ms. WIMP as indicated 31 January 2003 Johns Hopkins 19

Conclusions • Extra Dimensions yield natural dark matter candidates • Several novel features: – s-channel enhancements from degeneracy – Annihilation not chirality suppressed • Direct detection, m from n, e+, and g rays, may all push sensitivity beyond collider reach • super. WIMPs: graviton (and gravitino) DM naturally yields desired thermal relic density, but is inaccessible to all conventional searches • Much work to be done: n 1, h 1 WIMPs, many other possible NLKPs in super. WIMP scenarios, etc. • DM from extra dimensions – escape from the tyranny of neutralino dark matter! 31 January 2003 Johns Hopkins 20