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1.
Phys Rev Lett ; 115(17): 171803, 2015 Oct 23.
Article in English | MEDLINE | ID: mdl-26551103

ABSTRACT

We calculate the spin-independent scattering cross section for direct detection that results from the electromagnetic polarizability of a composite scalar "stealth baryon" dark matter candidate, arising from a dark SU(4) confining gauge theory-"stealth dark matter." In the nonrelativistic limit, electromagnetic polarizability proceeds through a dimension-7 interaction leading to a very small scattering cross section for dark matter with weak-scale masses. This represents a lower bound on the scattering cross section for composite dark matter theories with electromagnetically charged constituents. We carry out lattice calculations of the polarizability for the lightest "baryon" states in SU(3) and SU(4) gauge theories using the background field method on quenched configurations. We find the polarizabilities of SU(3) and SU(4) to be comparable (within about 50%) normalized to the stealth baryon mass, which is suggestive for extensions to larger SU(N) groups. The resulting scattering cross sections with a xenon target are shown to be potentially detectable in the dark matter mass range of about 200-700 GeV, where the lower bound is from the existing LUX constraint while the upper bound is the coherent neutrino background. Significant uncertainties in the cross section remain due to the more complicated interaction of the polarizablity operator with nuclear structure; however, the steep dependence on the dark matter mass, 1/m(B)(6), suggests the observable dark matter mass range is not appreciably modified. We briefly highlight collider searches for the mesons in the theory as well as the indirect astrophysical effects that may also provide excellent probes of stealth dark matter.

2.
Phys Rev Lett ; 112(11): 111601, 2014 Mar 21.
Article in English | MEDLINE | ID: mdl-24702347

ABSTRACT

Using lattice simulations, we study the infrared behavior of a particularly interesting SU(2) gauge theory, with six massless Dirac fermions in the fundamental representation. We compute the running gauge coupling derived nonperturbatively from the Schrödinger functional of the theory, finding no evidence for an infrared fixed point up through gauge couplings g(2) of order 20. This implies that the theory either is governed in the infrared by a fixed point of considerable strength, unseen so far in nonsupersymmetric gauge theories, or breaks its global chiral symmetries producing a large number of composite Nambu-Goldstone bosons relative to the number of underlying degrees of freedom. Thus either of these phases exhibits novel behavior.

3.
Phys Rev Lett ; 106(23): 231601, 2011 Jun 10.
Article in English | MEDLINE | ID: mdl-21770495

ABSTRACT

We describe a lattice simulation of the masses and decay constants of the lowest-lying vector and axial resonances, and the electroweak S parameter, in an SU(3) gauge theory with N(f)=2 and 6 fermions in the fundamental representation. The spectrum becomes more parity doubled and the S parameter per electroweak doublet decreases when N(f) is increased from 2 to 6, motivating study of these trends as N(f) is increased further, toward the critical value for transition from confinement to infrared conformality.

4.
Phys Rev Lett ; 104(7): 071601, 2010 Feb 19.
Article in English | MEDLINE | ID: mdl-20366870

ABSTRACT

We study the chiral properties of an SU(3) gauge theory with N{f} massless Dirac fermions in the fundamental representation when N{f} is increased from 2 to 6. For N{f}=2, our lattice simulations lead to a value of psi psi/F{3}, where F is the Nambu-Goldstone-boson decay constant and psi psi is the chiral condensate, which agrees with the measured QCD value. For N{f}=6, this ratio shows significant enhancement, presaging an even larger enhancement anticipated as N{f} increases further, toward the critical value for transition from confinement to infrared conformality.

5.
Phys Rev Lett ; 77(7): 1214-1217, 1996 Aug 12.
Article in English | MEDLINE | ID: mdl-10063020
6.
Phys Rev D Part Fields ; 53(5): 2789-2797, 1996 Mar 01.
Article in English | MEDLINE | ID: mdl-10020271
8.
Phys Rev Lett ; 75(11): 2081-2084, 1995 Sep 11.
Article in English | MEDLINE | ID: mdl-10059209
9.
Phys Rev D Part Fields ; 51(1): 240-250, 1995 Jan 01.
Article in English | MEDLINE | ID: mdl-10018291
10.
Phys Rev D Part Fields ; 50(3): 2116-2126, 1994 Aug 01.
Article in English | MEDLINE | ID: mdl-10017842
11.
Phys Rev D Part Fields ; 48(7): 3235-3241, 1993 Oct 01.
Article in English | MEDLINE | ID: mdl-10016579
12.
Phys Rev Lett ; 71(6): 823-826, 1993 Aug 09.
Article in English | MEDLINE | ID: mdl-10055377
13.
Phys Rev D Part Fields ; 47(7): 3075-3078, 1993 Apr 01.
Article in English | MEDLINE | ID: mdl-10015919
14.
Phys Rev Lett ; 69(19): 2750-2753, 1992 Nov 09.
Article in English | MEDLINE | ID: mdl-10046579
15.
Phys Rev D Part Fields ; 44(3): 871-877, 1991 Aug 01.
Article in English | MEDLINE | ID: mdl-10013941
16.
17.
Phys Rev D Part Fields ; 41(10): 3192-3196, 1990 May 15.
Article in English | MEDLINE | ID: mdl-10012247
18.
Phys Rev Lett ; 64(7): 721-724, 1990 Feb 12.
Article in English | MEDLINE | ID: mdl-10042061
19.
Phys Rev Lett ; 61(14): 1553-1556, 1988 Oct 03.
Article in English | MEDLINE | ID: mdl-10038835
20.
Phys Rev Lett ; 60(25): 2575-2578, 1988 Jun 20.
Article in English | MEDLINE | ID: mdl-10038394
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