Composite Dark Matter
George T. Fleming Yale University E. Rinaldi LLNL
Sakata-Hirata Hall, Nagoya University March 4, 2015
Lattice Strong Dynamics Collaboration Xiao-Yong Jin [LSD collab., Phys. Rev. D88 (2013) 014502] [LSD collab., Phys. Rev. D89 (2014) 094508] + LSD collab., in preparation (x2) Outline
• Motivations for searches of composite dark matter
• Features of strongly-coupled composite dark matter
• Searches for a class of models interesting for phenomenology
• Importance of lattice field theory simulations
• Lower bounds on composite dark matter models BSM Is Out There
• Discovery of SM-like Higgs boson doesn’t mean BSM physics is dead:
➡ What is the meaning of the hierarchy problem and naturalness?
➡ What solves the strong CP problem?
➡ What explains the matter-antimatter asymmetry? BSM Is Out There
• Discovery of SM-like Higgs boson doesn’t mean BSM physics is dead:
➡ What is the meaning of the hierarchy problem and naturalness?
➡ What solves the strong CP problem?
➡ What explains the matter-antimatter asymmetry?
➡ What is dark matter? Can it couple to the standard model? Is the mass scale related to the EW Higgs mechanism? Is it self-interacting? The gravity of Dark Matter
?????? New We Are Here Physics!! (QCD, EM, SM, etc.)
How do we know Dark Matter is there? Rotational velocity Curves of Galaxies
Gravitational Lensing
Cosmological Backgrounds The gravity of Dark Matter
?????? New We Are Here Physics!! (QCD, EM, SM, etc.) [Planck and ESA]
How do we know Dark Matter is there? Rotational velocity Curves of Galaxies
Gravitational Lensing
Cosmological Backgrounds The gravity of Dark Matter
?????? New We Are Here Physics!! (QCD, EM, SM, etc.) [Planck and ESA]
How do we know Dark Matter is there? Rotational velocity Curves of Galaxies
Gravitational Lensing Gravitational Interactions Cosmological Backgrounds Problems? Problems?
• Number of observed dwarf galaxies is inconsistent with predictions from dark matter simulations “Missing Satellites” Problems?
• Number of observed dwarf galaxies is inconsistent with predictions from dark matter simulations “Missing Satellites”
• Predicted dwarf galaxies are too dense “Too Big To Fail” Problems?
• Number of observed dwarf galaxies is inconsistent with predictions from dark matter simulations “Missing Satellites”
• Predicted dwarf galaxies are too dense “Too Big To Fail”
• Density profiles of dwarf galaxies is more cored than in simulations “Cusp vs. Core” Problems?
• Number of observed dwarf galaxies is inconsistent with predictions from dark matter simulations “Missing Satellites”
• Predicted dwarf galaxies are too dense “Too Big To Fail”
• Density profiles of dwarf galaxies is more cored than in simulations “Cusp vs. Core”
ameliorated by Self-Interacting Dark Matter Self-Interacting Dark Matter • In ΛCDM, galactic sub-halos have very dense, cuspy cores.
• Any dwarf galaxies residing in a cuspy sub-halo will be smaller and dimmer than in a sub-halo with more uniform density.
• Larger Milky Way and Andromeda dwarf galaxies are too bright for their expected sub-halos, if those sub-halos are made of non-interacting dark matter (ΛCDM). Self-interacting dark matter (SIDM) will make sub-halo cores less dense, enabling larger dwarf galaxies.
2 1 1 (v )/M 0.5 – 50 cm g ,v 10 – 100 km s rms ⇠ rms ' O. D. Elbert et al., arXiv:1412.1477 [astro-ph.GA] Self-Interacting Dark Matter
Strongly-Coupled Composite Dark Matter
interactions with SM particles that can evade current experimental constraints View from Snowmass (I)
R-parity NMSSM MSSM violating
WIMPless DM Supersymmetry Hidden Sector DM Gravitino DM mSUGRA Self-Interacting DM pMSSM
Q-balls Techni- baryons Dark Photon R-parity Conserving Dirac Asymmetric DM DM
Light Extra Dimensions Dynamical Force Carriers DM
Warm DM Solitonic DM UED DM
Sterile Neutrinos Quark 6d Warped Extra Nuggets Dimensions 5d
RS DM T-odd DM Axion DM ?
Little Higgs QCD Axions
Axion-like Particles T Tait Littlest Higgs
Snowmass 2013: The Cosmic Frontier [arXiv:1401.6085]
Where is composite dark matter? View from Snowmass (I)
R-parity NMSSM MSSM violating
WIMPless DM Supersymmetry Hidden Sector DM Gravitino DM mSUGRA Self-Interacting DM pMSSM
Q-balls Techni- baryons Dark Photon R-parity Conserving Dirac Asymmetric DM DM
Light Extra Dimensions Dynamical Force Carriers DM
Warm DM Solitonic DM UED DM
Sterile Neutrinos Quark 6d Warped Extra Nuggets Dimensions 5d
RS DM T-odd DM Axion DM ?
Little Higgs QCD Axions
Axion-like Particles T Tait Littlest Higgs
Snowmass 2013: The Cosmic Frontier [arXiv:1401.6085]
Where is composite dark matter? View from Snowmass (II)
SuperCDMS Soudan CDMS-lite SuperCDMS Soudan Low Threshold XENON 10 S2 (2013) 10!39 CDMS-II Ge Low Threshold (2011) 10!3 CoGeNT PICO250-C3F8 !40 (2012) !4 10 CDMS Si 10 (2013)
# ! ! 41 5 # 2 10 DAMA SIMPLE (2012) 10
COUPP (2012) pb cm !
! !42 CRESST !6 10 ZEPLIN-III (2012) 10 SuperCDMS !43 CDMS II Ge (2009) !7 10 EDELWEISS (2011) 10 SNOLAB SuperCDMS Soudan section section N EU TR Xenon100 (2012) !44 IN DarkSide 50 !8 10 O 10 7Be C TT LUX OHE SCA ER cross cross R NT I Neutrinos E 8 N !45 B G PICO250-CF3I !9 10 Neutrinos 10 Xenon1T
!46 DEAP3600 !10 10 DarkSide G2 10 LZ nucleon nucleon
! ! !47 !11 10 (Green&ovals)&Asymmetric&DM&& 10 (Violet&oval)&Magne7c&DM& RING ATTE !48 (Blue&oval)&Extra&dimensions&& NT SC !12
E WIMP HER WIMP 10 (Red&circle)&SUSY&MSSM& CO 10 RINO &&&&&MSSM:&Pure&Higgsino&& NEUT !49 !13 10 &&&&&MSSM:&A&funnel& Atmospheric and DSNB Neutrinos 10 &&&&&MSSM:&BinoEstop&coannihila7on& !50 &&&&&MSSM:&BinoEsquark&coannihila7on& !14 10 & 10 1 10 100 1000 104 WIMP Mass GeV c2
Snowmass 2013: The Cosmic Frontier [arXiv:1401.6085] ! " # Partial wave unitarity? Where is composite dark matter? View from Snowmass (II)
SuperCDMS Soudan CDMS-lite SuperCDMS Soudan Low Threshold XENON 10 S2 (2013) 10!39 CDMS-II Ge Low Threshold (2011) 10!3 CoGeNT PICO250-C3F8 !40 (2012) !4 10 CDMS Si 10 (2013)
# ! ! 41 5 # 2 10 DAMA SIMPLE (2012) 10
COUPP (2012) pb cm !
! !42 CRESST !6 10 ZEPLIN-III (2012) 10 SuperCDMS !43 CDMS II Ge (2009) !7 10 EDELWEISS (2011) 10 SNOLAB SuperCDMS Soudan section section N EU TR Xenon100 (2012) !44 IN DarkSide 50 !8 10 O 10 7Be C TT LUX Dark SU(3) Baryon OHE SCA ER cross cross R NT I Neutrinos E 8 N !45 B G PICO250-CF3I !9 10 Neutrinos 10 Xenon1T
!46 DEAP3600 !10 10 DarkSide G2 10 LZ nucleon nucleon
! ! !47 !11 10 (Green&ovals)&Asymmetric&DM&& 10 (Violet&oval)&Magne7c&DM& RING ATTE !48 (Blue&oval)&Extra&dimensions&& NT SC !12
E WIMP HER WIMP 10 (Red&circle)&SUSY&MSSM& CO 10 RINO &&&&&MSSM:&Pure&Higgsino&& NEUT !49 !13 10 &&&&&MSSM:&A&funnel& Atmospheric and DSNB Neutrinos 10 &&&&&MSSM:&BinoEstop&coannihila7on& !50 &&&&&MSSM:&BinoEsquark&coannihila7on& !14 10 & 10 1 10 100 1000 104 WIMP Mass GeV c2
Snowmass 2013: The Cosmic Frontier [arXiv:1401.6085] ! " # Partial wave unitarity? Where is composite dark matter? Strongly-coupled composite dark matter
• Dark matter is a composite object
• Composite object is electroweak neutral
• Constituents can have electroweak charges
• Dark matter is stable thanks to a global symmetry (like baryon number) Strongly-coupled composite dark matter
• Dark matter is a composite object Akin to a technibaryon
• Composite object is electroweak neutral
• Constituents can have electroweak charges
• Dark matter is stable thanks to a global symmetry (like baryon number) Strongly-coupled composite dark matter
• Dark matter is a composite object Akin to a technibaryon
• Composite object is electroweak neutral Suppressed interactions with SM
• Constituents can have electroweak charges
• Dark matter is stable thanks to a global symmetry (like baryon number) Strongly-coupled composite dark matter
• Dark matter is a composite object Akin to a technibaryon
• Composite object is electroweak neutral Suppressed interactions with SM
• Constituents can have electroweak charges Mechanisms to provide observed relic abundance • Dark matter is stable thanks to a global symmetry (like baryon number) Strongly-coupled composite dark matter
• Dark matter is a composite object Akin to a technibaryon
• Composite object is electroweak neutral Suppressed interactions with SM
• Constituents can have electroweak charges Mechanisms to provide observed relic abundance • Dark matter is stable thanks to a global symmetry (like baryon number) Guaranteed in many models What do we have in mind? • In general we think about a new strongly-coupled gauge sector like QCD with a plethora of composite states in the spectrum
• Dark fermions have dark color and also have electroweak charges
• Depending on the model, dark fermions have electroweak breaking masses (chiral), electroweak preserving masses (vector) or a mixture
• A global symmetry of the theory naturally stabilizes the dark baryonic composite states (e.g. neutron) What do we have in mind? • In general we think about a new strongly-coupled gauge sector like QCD with a plethora of composite states in the spectrum
• Dark fermions have dark color and also have electroweak charges
• Depending on the model, dark fermions have electroweak breaking masses (chiral), electroweak preserving masses (vector) or a mixture
• A global symmetry of the theory naturally stabilizes the dark baryonic composite states (e.g. neutron) we construct a minimal model with these features “How dark is Dark Matter?”
Interactions of neutral object with photons + Higgs
• dimension 4 ➥ Higgs exchange
µ⌫ (¯ )Fµ⌫ • ➥ dimension 5 magnetic dipole ⇤dark
µ⌫ (¯ )vµ@⌫ F • dimension 6 ➥ charge radius 2 ⇤dark
µ⌫ (¯ )Fµ⌫ F • dimension 7 ➥ polarizability 3 ⇤dark “How dark is Dark Matter?”
Interactions of neutral object with photons + Higgs
• dimension 4 ➥ Higgs exchange
µ⌫ (¯ )Fµ⌫ • ➥ dimension 5 magnetic dipole ⇤dark
µ⌫ (¯ )vµ@⌫ F • dimension 6 ➥ charge radius 2 ⇤dark
µ⌫ (¯ )Fµ⌫ F • dimension 7 ➥ polarizability 3 ⇤dark “How dark is Dark Matter?”
Interactions of neutral object with photons + Higgs
• dimension 4 ➥ Higgs exchange
µ⌫ (¯ )Fµ⌫ • ➥ dimension 5 magnetic dipole ⇤dark
µ⌫ (¯ )vµ@⌫ F • dimension 6 ➥ charge radius 2 ⇤dark
µ⌫ (¯ )Fµ⌫ F • dimension 7 ➥ polarizability 3 ⇤dark “How dark is Dark Matter?”
Interactions of neutral object with photons + Higgs
• dimension 4 ➥ Higgs exchange
µ⌫ (¯ )Fµ⌫ • ➥ dimension 5 magnetic dipole ⇤dark
µ⌫ (¯ )vµ@⌫ F • dimension 6 ➥ charge radius 2 ⇤dark
µ⌫ (¯ )Fµ⌫ F • dimension 7 ➥ polarizability 3 ⇤dark Coupling Dark Baryons to SM
ψ σ (ψψ) (ψψ) F Mag. Moment Charge Radius Polarizability dim. 5 dim. 6 dim. 7
Odd N ✔ ✔ ✔ No Flavor Sym.
Odd N ✔ Flavor Sym
Even N ✔ ✔ No Flavor Sym.
Even N ✔ Flavor Sym. [LSD collab., Phys. Rev. D88 (2013) 014502] MagneticMagnetic moment moment anddominates for MB & 25 GeV —Dashed lines show charge radius r 2 contribution to full rate —Suppressed by 1/M2 relative to magnetic moment contribution charge radius of BDM ⌦ ↵ SU(3) model: DM is neutral baryon with spin 1/2 104 102
100
2 XENON100 results 10 day) • Need non-perturbative · 2 4 only sensitive to r calculation of form-factors 10 6 10 for MB . 0.5 TeV for DM composite object ⌦ ↵ 8 10
Rate, event10 / (kg 10 • Negligible dependence 12 ( . ) 10 Estimate MB . 0 01 TeV on constituent mass and Nf =2 O 14 Nf =6 10 sensitive to polarizability number of flavors XENON100 [1207.5988], 95% CL exclusion 16 10 2 1 0 1 2 10 10 10 10 10 M = MB [TeV] • Magnetic moment dominates for masses = 0 automatically for SU(N) gauge theories with even N... > 25GeV Composite dark matter on the lattice Theory Seminar, 24 March 2014 13 / 20 [LSD collab., Phys. Rev. D88 (2013) 014502] MagneticMagnetic moment moment anddominates for MB & 25 GeV —Dashed lines show charge radius r 2 contribution to full rate —Suppressed by 1/M2 relative to magnetic moment contribution charge radius of BDM ⌦ ↵ SU(3) model: DM is neutral baryon with spin 1/2 104 102
100
2 XENON100 results 10 day) • Need non-perturbative · 2 4 only sensitive to r calculation of form-factors 10 6 10 for MB . 0.5 TeV for DM composite object ⌦ ↵ 8 10
Rate, event10 / (kg 10 • Negligible dependence 12 ( . ) 10 Estimate MB . 0 01 TeV on constituent mass and Nf =2 O 14 Nf =6 10 sensitive to polarizability number of flavors XENON100 [1207.5988], 95% CL exclusion 16 10 2 1 0 1 2 10 10 10 10 10 M = MB [TeV] • Magnetic moment dominates for masses = 0 automatically for SU(N) gauge theories with even N... without magnetic > 25GeV moment contribution Composite dark matter on the lattice Theory Seminar, 24 March 2014 13 / 20 [LSD collab., Phys. Rev. D88 (2013) 014502] MagneticMagnetic moment moment anddominates for MB & 25 GeV —Dashed lines show charge radius r 2 contribution to full rate —Suppressed by 1/M2 relative to magnetic moment contribution charge radius of BDM ⌦ ↵ SU(3) model: DM is neutral baryon with spin 1/2 104 102
100
2 XENON100 results 10 day) • Need non-perturbative · 2 4 only sensitive to r calculation of form-factors 10 6 10 for MB . 0.5 TeV for DM composite object ⌦ ↵ 8 10
Rate, event10 / (kg 10 • Negligible dependence 12 ( . ) 10 Estimate MB . 0 01 TeV on constituent mass and Nf =2 O 14 Nf =6 10 sensitive to polarizability number of flavors XENON100 [1207.5988], 95% CL exclusion 16 10 2 1 0 1 2 10 10 10 10 10 M = MB [TeV] • Magnetic moment dominates for masses = 0 automatically for SU(N) gauge theories with even N... without magnetic > 25GeV moment contribution Excludes dark matter Composite dark matter on the latticemass below 10 TeV! Theory Seminar, 24 March 2014 13 / 20 [LSD collab., in preparation] “Stealth Dark Matter” model
3
• Let’s focus on a SU(N) dark gauge Field SU(N)D (SU(2)L, Y ) Q will be identified with U(1)Y , and one U(1) will be iden- u tified with dark baryon number. The total fermionic con- F1 +1/2 sector with N=4 F1 = N (2, 0) tent of the model is therefore 8 Weyl fermions that pair F d ! 1/2 ! 1 u up to become 4 Dirac fermions in the fundamental or F2 +1/2 F2 = N (2, 0) anti-fundamental representation of SU(N)D with electric • Let dark fermions interact with the F d ! 1/2 ! Q T + Y = 1/2 2 charges of 3,L . We use the notation u ⌘ ± u d u F3 N (1, +1/2) +1/2 where the superscript u and d (as in F , F and later , SM Higgs and obtain current/chiral d u d F d N (1, 1/2) 1/2 , , ) to denote a fermion with electric charge of 3 masses u Q =1/2 and Q = 1/2 respectively. F4 N (1, +1/2) +1/2 d The fermion kinetic terms in the Lagrangian are given F4 N (1, 1/2) 1/2 by • Let’s introduce vector-like masses
µ j† µ j j for dark fermions that do not break TABLE I. Fermion particle content of the composite dark matter = iF † ¯ Di,µFi + iF ¯ D F , L i i i,µ i model. All fields are two-component (Weyl) spinors. SU(2)L i=1,2 i=3,4;j=u,d EW symmetry refers to the standard model electroweak gauge group, and Y is X X (1) the hypercharge. The electric charge Q = T3 + Y for the fermion where the covariant derivatives are components is shown for completeness. D @ igW a a/2 ig Gb tb (2) 1,µ ⌘ µ µ D µ D @ igW a a/2+ig Gb tb⇤ (3) yet have the ability to simulate on the lattice. Naive di- 2,µ ⌘ µ µ D µ j j b b mensional analysis applied to the annihilation rate suggests D3,µ @µ ig0Y Bµ igDG t (4) > ⌘ µ the dark matter mass scale should be 10-100 TeV, but a j j b b D @ ig0Y B + ig G t ⇤ (5) more precise estimate is not possible⇠ at this time. In any 4,µ ⌘ µ µ D µ case, for dark matter with mass below this value, there is with the interactions among the electroweak group and the an underproduction of dark matter through the symmet- u d b new SU(N)D. Here Y =1/2, Y = 1/2 and t ric thermal relic mechanism, and so this does not restrict are the representation matrices for the fundamental N of consideration of dark matter mass scales between the elec- SU(N) . troweak scale up to this thermal abundance bound. D The vector-like mass terms allowed by the gauge sym- metries are
CONSTRUCTING A VIABLE MODEL M ✏ F iF j M u F uF d +M d F dF u +h.c., (6) L 12 ij 1 2 34 3 4 34 3 4 12 [placeholder for a description of how a viable model where ✏12 ✏ud = 1= ✏ and the relative minus with interactions with the Higgs can be constructed while signs between⌘ the mass terms have been chosen for later satisfying the various (gross) experimental constraints] convenience. The mass term M12 explicitly breaks the [SU(2) U(1)]2 global symmetry down to the diagonal ⇥ We consider a new, strongly-coupled SU(N)D gauge SU(2)diag U(1) where the SU(2)diag is identified with ⇥ u,d group with fermionic matter in the vector-like representa- SU(2)L. The mass terms M34 explicitly break the re- tions shown in Table I. maining [SU(2) U(1)]2 down to U(1) U(1) where one ⇥ ⇥ of the U(1)’s is identified with U(1)Y . (In the special case u d This is not the only possible choice for the charges, but when M34 = M34, the global symmetry is accidentally en- the requirement for the presence of Higgs Yukawa cou- hanced to SU(2) U(1), where the global SU(2) acts as a plings, along with extremely strong bounds on the ex- custodial symmetry.)⇥ Thus, after weakly gauging the elec- istence of stable fractionally-charged particles based on troweak symmetry and writing arbitrary vector-like mass searches for rare isotopes [? ], greatly constrains the num- terms, the unbroken flavor symmetry is thus U(1) U(1). ⇥ ber of possible models. Electroweak symmetry breaking mass terms arise from coupling to the Higgs field H that we take to be in the (2, +1/2) representation. They are given by DARK FERMION INTERACTIONS AND MASSES u i j d d u y14✏ijF1H F4 + y14F1 H†F4 u,d L d i j d u · u The fermions Fi transform under a global U(4) y23✏ijF2H F3 y23F2 H†F3 + h.c., (7) U(4) flavor symmetry that is broken to [SU(2) U(1)⇥]4 · by the weak gauging of the electroweak symmetry.⇥ From where again the relative minus signs are chosen for later this large global symmetry, one SU(2) (diagonal) sub- convenience. After electroweak symmetry breaking, H = group will be identified with SU(2) , one U(1) subgroup (0 v/p2)T , with v 246 GeV. Inserting the vev L ' [LSD collab., in preparation] “Stealth Dark Matter” model
3
• Let’s focus on a SU(N) dark gauge Field SU(N)D (SU(2)L, Y ) Q will be identified with U(1)Y , and one U(1) will be iden- u tified with dark baryon number. The total fermionic con- F1 +1/2 sector with N=4 F1 = N (2, 0) tent of the model is therefore 8 Weyl fermions that pair F d ! 1/2 ! 1 u up to become 4 Dirac fermions in the fundamental or F2 +1/2 F2 = N (2, 0) anti-fundamental representation of SU(N)D with electric • Let dark fermions interact with the F d ! 1/2 ! Q T + Y = 1/2 2 charges of 3,L . We use the notation u ⌘ ± u d u F3 N (1, +1/2) +1/2 where the superscript u and d (as in F , F and later , SM Higgs and obtain current/chiral d u d F d N (1, 1/2) 1/2 , , ) to denote a fermion with electric charge of 3 masses u Q =1/2 and Q = 1/2 respectively. F4 N (1, +1/2) +1/2 d The fermion kinetic terms in the Lagrangian are given F4 N (1, 1/2) 1/2 by • Let’s introduce vector-like masses
µ j† µ j j for dark fermions that do not break TABLE I. Fermion particle content of the composite dark matter = iF † ¯ Di,µFi + iF ¯ D F , L i i i,µ i model. All fields are two-component (Weyl) spinors. SU(2)L i=1,2 i=3,4;j=u,d EW symmetry refers to the standardu modeli j electroweakd d gauge group,u and Y is X X + y14✏ijF1H F4 + y14F1 H†F4 (1) the hypercharge.L The electric charge Q = T ·+ Y for the fermion d i j d u 3 u where the covariant derivatives are components isy shown23✏ijF for2H completeness.F3 y23F2 H†F3 + h.c. · D @ igW a a/2 ig Gb tb (2) 1,µ ⌘ µ µ D µ D @ igW a a/2+ig Gb tb⇤ (3) yet have the ability to simulate on the lattice. Naive di- 2,µ ⌘ µ µ D µ j j b b mensional analysis applied to the annihilation rate suggests D3,µ @µ ig0Y Bµ igDG t (4) > ⌘ µ the dark matter mass scale should be 10-100 TeV, but a j j b b D @ ig0Y B + ig G t ⇤ (5) more precise estimate is not possible⇠ at this time. In any 4,µ ⌘ µ µ D µ case, for dark matter with mass below this value, there is with the interactions among the electroweak group and the an underproduction of dark matter through the symmet- u d b new SU(N)D. Here Y =1/2, Y = 1/2 and t ric thermal relic mechanism, and so this does not restrict are the representation matrices for the fundamental N of consideration of dark matter mass scales between the elec- SU(N) . troweak scale up to this thermal abundance bound. D The vector-like mass terms allowed by the gauge sym- metries are
CONSTRUCTING A VIABLE MODEL M ✏ F iF j M u F uF d +M d F dF u +h.c., (6) L 12 ij 1 2 34 3 4 34 3 4 12 [placeholder for a description of how a viable model where ✏12 ✏ud = 1= ✏ and the relative minus with interactions with the Higgs can be constructed while signs between⌘ the mass terms have been chosen for later satisfying the various (gross) experimental constraints] convenience. The mass term M12 explicitly breaks the [SU(2) U(1)]2 global symmetry down to the diagonal ⇥ We consider a new, strongly-coupled SU(N)D gauge SU(2)diag U(1) where the SU(2)diag is identified with ⇥ u,d group with fermionic matter in the vector-like representa- SU(2)L. The mass terms M34 explicitly break the re- tions shown in Table I. maining [SU(2) U(1)]2 down to U(1) U(1) where one ⇥ ⇥ of the U(1)’s is identified with U(1)Y . (In the special case u d This is not the only possible choice for the charges, but when M34 = M34, the global symmetry is accidentally en- the requirement for the presence of Higgs Yukawa cou- hanced to SU(2) U(1), where the global SU(2) acts as a plings, along with extremely strong bounds on the ex- custodial symmetry.)⇥ Thus, after weakly gauging the elec- istence of stable fractionally-charged particles based on troweak symmetry and writing arbitrary vector-like mass searches for rare isotopes [? ], greatly constrains the num- terms, the unbroken flavor symmetry is thus U(1) U(1). ⇥ ber of possible models. Electroweak symmetry breaking mass terms arise from coupling to the Higgs field H that we take to be in the (2, +1/2) representation. They are given by DARK FERMION INTERACTIONS AND MASSES u i j d d u y14✏ijF1H F4 + y14F1 H†F4 u,d L d i j d u · u The fermions Fi transform under a global U(4) y23✏ijF2H F3 y23F2 H†F3 + h.c., (7) U(4) flavor symmetry that is broken to [SU(2) U(1)⇥]4 · by the weak gauging of the electroweak symmetry.⇥ From where again the relative minus signs are chosen for later this large global symmetry, one SU(2) (diagonal) sub- convenience. After electroweak symmetry breaking, H = group will be identified with SU(2) , one U(1) subgroup (0 v/p2)T , with v 246 GeV. Inserting the vev L ' [LSD collab., in preparation] “Stealth Dark Matter” model
3
• Let’s focus on a SU(N) dark gauge Field SU(N)D (SU(2)L, Y ) Q will be identified with U(1)Y , and one U(1) will be iden- u tified with dark baryon number. The total fermionic con- F1 +1/2 sector with N=4 F1 = N (2, 0) tent of the model is therefore 8 Weyl fermions that pair F d ! 1/2 ! 1 u up to become 4 Dirac fermions in the fundamental or F2 +1/2 F2 = N (2, 0) anti-fundamental representation of SU(N)D with electric • Let dark fermions interact with the F d ! 1/2 ! Q T + Y = 1/2 2 charges of 3,L . We use the notation u ⌘ ± u d u F3 N (1, +1/2) +1/2 where the superscript u and d (as in F , F and later , SM Higgs and obtain current/chiral d u d F d N (1, 1/2) 1/2 , , ) to denote a fermion with electric charge of 3 masses u Q =1/2 and Q = 1/2 respectively. F4 N (1, +1/2) +1/2 d The fermion kinetic terms in the Lagrangian are given F4 N (1, 1/2) 1/2 by • Let’s introduce vector-like masses
µ j† µ j j for dark fermions that do not break TABLE I. Fermion particle content of the composite dark matter = iF † ¯ Di,µFi + iF ¯ D F , L i i i,µ i model. All fields are two-component (Weyl) spinors. SU(2)L i=1,2 i=3,4;j=u,d EW symmetry refers to the standardu modeli j electroweakd d gauge group,u and Y is X X + y14✏ijF1H F4 + y14F1 H†F4 (1) the hypercharge.L The electric charge Q = T ·+ Y for the fermion d i j d u 3 u where the covariant derivatives are components isy shown23✏ijF for2H completeness.F3 y23F2 H†F3 + h.c. · D @ igW a a/2 ig Gb tb (2) 1,µ ⌘ µ µ D µ D @ igW a a/2+ig Gb tb⇤ (3) yet have the ability to simulate on the lattice. Naive di- 2,µ ⌘ µ µ D µ i j u u d d d u j j b b M12✏ijF1mensionalF2 M34 analysisF3 F4 applied+ M34 toF3 theF4 annihilation+ h.c. rate suggests D3,µ @µ ig0Y Bµ igDG t (4) L > ⌘ µ the dark matter mass scale should be 10-100 TeV, but a j j b b D @ ig0Y B + ig G t ⇤ (5) more precise estimate is not possible⇠ at this time. In any 4,µ ⌘ µ µ D µ case, for dark matter with mass below this value, there is with the interactions among the electroweak group and the an underproduction of dark matter through the symmet- u d b new SU(N)D. Here Y =1/2, Y = 1/2 and t ric thermal relic mechanism, and so this does not restrict are the representation matrices for the fundamental N of consideration of dark matter mass scales between the elec- SU(N) . troweak scale up to this thermal abundance bound. D The vector-like mass terms allowed by the gauge sym- metries are
CONSTRUCTING A VIABLE MODEL M ✏ F iF j M u F uF d +M d F dF u +h.c., (6) L 12 ij 1 2 34 3 4 34 3 4 12 [placeholder for a description of how a viable model where ✏12 ✏ud = 1= ✏ and the relative minus with interactions with the Higgs can be constructed while signs between⌘ the mass terms have been chosen for later satisfying the various (gross) experimental constraints] convenience. The mass term M12 explicitly breaks the [SU(2) U(1)]2 global symmetry down to the diagonal ⇥ We consider a new, strongly-coupled SU(N)D gauge SU(2)diag U(1) where the SU(2)diag is identified with ⇥ u,d group with fermionic matter in the vector-like representa- SU(2)L. The mass terms M34 explicitly break the re- tions shown in Table I. maining [SU(2) U(1)]2 down to U(1) U(1) where one ⇥ ⇥ of the U(1)’s is identified with U(1)Y . (In the special case u d This is not the only possible choice for the charges, but when M34 = M34, the global symmetry is accidentally en- the requirement for the presence of Higgs Yukawa cou- hanced to SU(2) U(1), where the global SU(2) acts as a plings, along with extremely strong bounds on the ex- custodial symmetry.)⇥ Thus, after weakly gauging the elec- istence of stable fractionally-charged particles based on troweak symmetry and writing arbitrary vector-like mass searches for rare isotopes [? ], greatly constrains the num- terms, the unbroken flavor symmetry is thus U(1) U(1). ⇥ ber of possible models. Electroweak symmetry breaking mass terms arise from coupling to the Higgs field H that we take to be in the (2, +1/2) representation. They are given by DARK FERMION INTERACTIONS AND MASSES u i j d d u y14✏ijF1H F4 + y14F1 H†F4 u,d L d i j d u · u The fermions Fi transform under a global U(4) y23✏ijF2H F3 y23F2 H†F3 + h.c., (7) U(4) flavor symmetry that is broken to [SU(2) U(1)⇥]4 · by the weak gauging of the electroweak symmetry.⇥ From where again the relative minus signs are chosen for later this large global symmetry, one SU(2) (diagonal) sub- convenience. After electroweak symmetry breaking, H = group will be identified with SU(2) , one U(1) subgroup (0 v/p2)T , with v 246 GeV. Inserting the vev L ' [LSD collab., Phys. Rev. D89 (2014) 094508] Higgs exchange cross section in Stealth DM
• yh Need to non-perturbatively mf (h)=m + evaluate the σ-term of the dark p2 baryon (scalar nuclear form v @ mf (h) yv factor) ↵ = 1 ⌘ m @ h p f h=v 2m + yv • Effective Higgs coupling non- 5 ¥10-43 MPS MV=0.77 L trivial with mixed chiral and 2 !=0.64
cm -43
H 1 ¥10 vector-like masses 5 ¥10-44 ê !=0.16 section 1 ¥10-44 -45
• Model-dependent answer for the cross 5 ¥10 !=0.04 cross-section in this channels 1 ¥10-45
nucleon -46
- 5 ¥10
• DM !=0.01 A non-negligible vector mass is 1 ¥10-46 needed to evade direct 10 50 100 500 1000 detection bounds mB GeV
H L [LSD collab., Phys. Rev. D89 (2014) 094508] Higgs exchange cross section in Stealth DM
• yh Need to non-perturbatively mf (h)=m + evaluate the σ-term of the dark p2 baryon (scalar nuclear form v @ mf (h) yv factor) ↵ = 1 ⌘ m @ h p f h=v 2m + yv • Effective Higgs coupling non- 5 ¥10-43 MPS MV=0.77 L trivial with mixed chiral and 2 !=0.64
cm -43
H 1 ¥10 vector-like masses 5 ¥10-44 ê !=0.16 section 1 ¥10-44 -45
• Model-dependent answer for the cross 5 ¥10 !=0.04 cross-section in this channels 1 ¥10-45
nucleon -46
- 5 ¥10
• DM !=0.01 A non-negligible vector mass is 1 ¥10-46 needed to evade direct 10 50 100 500 1000 detection bounds mB GeV
LEP bound on charged pseudoscalar mesons H L LHC could be do better here. LUX bound [Phys. Rev. Lett. 112 (2014)] Electromagnetic polarizability
• remove magnetic dipole moment: