Dark matter at LHC and beyond Alejandro Ibarra ICTP, Trieste May - - PowerPoint PPT Presentation

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Dark matter at LHC and beyond Alejandro Ibarra ICTP, Trieste May - - PowerPoint PPT Presentation

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Dark matter at LHC and beyond Alejandro Ibarra ICTP, Trieste May 2019 There The re is e is evide vidence f for dark r dark mat matte ter r in a wide a wide rang range o of di distan ance s scale les Clusters Observable

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Dark matter at LHC and beyond

Alejandro Ibarra

ICTP, Trieste May 2019

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SLIDE 2

distance kpc Solar system Clusters

  • f galaxies

Observable Universe Mpc Gpc pc

The There re is e is evide vidence f for dark r dark mat matte ter r in a wide a wide rang range o

  • f di

distan ance s scale les

Galaxies

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SLIDE 3

distance kpc Solar system Clusters

  • f galaxies

Observable Universe Mpc Gpc pc Galaxies

The There re is e is evide vidence f for dark r dark mat matte ter r in a wide a wide rang range o

  • f di

distan ance s scale les

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SLIDE 4

distance kpc Solar system Clusters

  • f galaxies

Observable Universe Mpc Gpc pc Abell 1689 Galaxies

The There re is e is evide vidence f for dark r dark mat matte ter r in a wide a wide rang range o

  • f di

distan ance s scale les

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SLIDE 5

distance kpc Solar system Clusters

  • f galaxies

Observable Universe Mpc Gpc pc Abell 1689 Galaxies

The There re is e is evide vidence f for dark r dark mat matte ter r in a wide a wide rang range o

  • f di

distan ance s scale les

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SLIDE 6

distance kpc Solar system Clusters

  • f galaxies

Observable Universe Mpc Gpc pc Galaxies

The There re is e is evide vidence f for dark r dark mat matte ter r in a wide a wide rang range o

  • f di

distan ance s scale les

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SLIDE 7

distance kpc Solar system Clusters

  • f galaxies

Observable Universe Mpc Gpc pc Galaxies

The There re is e is evide vidence f for dark r dark mat matte ter r in a wide a wide rang range o

  • f di

distan ance s scale les

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SLIDE 8

distance kpc Solar system Clusters

  • f galaxies

Observable Universe Mpc Gpc pc Galaxies

Assumption, but well motivated

The There re is e is evide vidence f for dark r dark mat matte ter r in a wide a wide rang range o

  • f di

distan ance s scale les

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SLIDE 9
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FIMPs

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WIMP WIMPs at col s at colliders ders

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The freeze-out mechanism Assumption 1: Dark matter particles are stable

  • n cosmological timescales.
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SM SM DM DM

annihilation

The freeze-out mechanism

production scattering

Assumption 2: Dark matter particles interact in pairs with the Standard Model particles.

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SM SM DM DM

annihilation

The freeze-out mechanism

production scattering

Assumption 3: The WIMP interaction strength is large enough to keep the DM particles in thermal equilibrium with the SM plasma at very high temperatures

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SM SM DM DM

annihilation

The freeze-out mechanism

production scattering

Assumption 4: The WIMP interaction strength is small enough to allow DM particles to chemically decouple from the SM plasma sufficiently early.

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SM SM DM DM

annihilation

The freeze-out mechanism

production scattering Fraction of the total energy of the Universe in the form of DM

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SM SM DM DM

annihilation

The freeze-out mechanism

production scattering Correct DM abundance (25% of the total energy of the Universe), if

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SM SM DM DM

annihilation

The freeze-out mechanism

production scattering

~ weak interaction

Correct DM abundance (25% of the total energy of the Universe), if

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Ver Very at attrac ractiv ive f fram ramework rk:

1) Relatively few speculations from particle physics and from cosmology. Thermal freeze-out lies at the core of other (tested) phenomena in the early Universe

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Ver Very at attrac ractiv ive f fram ramework rk:

1) Relatively few speculations from particle physics and from cosmology. Thermal freeze-out lies at the core of other (tested) phenomena in the early Universe

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Ver Very at attrac ractiv ive f fram ramework rk:

1) Relatively few speculations from particle physics and from cosmology. Thermal freeze-out lies at the core of other (tested) phenomena in the early Universe

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Ver Very at attrac ractiv ive f fram ramework rk:

1) Relatively few speculations from particle physics and from cosmology. Thermal freeze-out lies at the core of other (tested) phenomena in the early Universe

?

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Ver Very at attrac ractiv ive f fram ramework rk:

1) Relatively few speculations from particle physics and from cosmology. Thermal freeze-out lies at the core of other (tested) phenomena in the early Universe 2) Potentially testable σ ~ 1 pb, for coupling ~ 0.01 – 0.1 and mass ~ 1 GeV – 1 TeV

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Ver Very at attrac ractiv ive f fram ramework rk:

1) Relatively few speculations from particle physics and from cosmology. Thermal freeze-out lies at the core of other (tested) phenomena in the early Universe 2) Potentially testable

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Ver Very at attrac ractiv ive f fram ramework rk:

1) Relatively few speculations from particle physics and from cosmology. Thermal freeze-out lies at the core of other (tested) phenomena in the early Universe 2) Potentially testable SM SM

annihilation

DM DM

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SLIDE 27

Ver Very at attrac ractiv ive f fram ramework rk:

1) Relatively few speculations from particle physics and from cosmology. Thermal freeze-out lies at the core of other (tested) phenomena in the early Universe 2) Potentially testable SM SM DM DM

s c a t t e r i n g

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Ver Very at attrac ractiv ive f fram ramework rk:

1) Relatively few speculations from particle physics and from cosmology. Thermal freeze-out lies at the core of other (tested) phenomena in the early Universe 2) Potentially testable SM SM DM DM

production

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Searching for WIMP dark matter at the LHC

Differential cross-section for the final state of interest Y

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Differential cross-section for the final state of interest Y Fraction of the momenta of the proton carried by the parton i

Searching for WIMP dark matter at the LHC

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Differential cross-section for the final state of interest Y Parton distribution functions

Ball et al'17

Searching for WIMP dark matter at the LHC

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Differential cross-section for the final state of interest Y Cross-section for the partonic process

Searching for WIMP dark matter at the LHC SM SM DM DM

annihilation production scattering

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Monojet + missing ET

Searching for WIMP dark matter at the LHC

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Monojet + missing ET

Searching for WIMP dark matter at the LHC

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Monojet + missing ET

Searching for WIMP dark matter at the LHC

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Comparison to direct detection experiments

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Astrophysical uncertainties in DD experiments

 The energy and luminosity of a collider is known

(information from colliders very robust)

 Dark matter direct search experiments, on the other hand,

suffer from astrophysical uncertainties

Differential rate of DM-induced scatterings

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Astrophysical uncertainties in DD experiments

 The energy and luminosity of a collider is known

(information from colliders very robust)

 Dark matter direct search experiments, on the other hand,

suffer from astrophysical uncertainties

Differential rate of DM-induced scatterings

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▪ “local measurements”:

 Local dark matter density?

▪ “global measurements”:

From extrapolations of

ρ( r ) determined from rotation curves at large r , to the position

  • f the Solar System.

From vertical kinematics

  • f stars near (~1 kpc) the Sun

Read '14

Astrophysical uncertainties in DD experiments

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Completely unknown. Rely on theoretical considerations

▪ If the density distribution follows a singular isothermal sphere profile, the velocity distribution has a Maxwell-Boltzmann form.

 Local dark matter velocity distribution?

Astrophysical uncertainties in DD experiments

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SLIDE 41

Completely unknown. Rely on theoretical considerations  Local dark matter velocity distribution?

▪ Dark matter-only simulations. Show deviations from Maxwell-Boltzmann ▪ If the density distribution follows a singular isothermal sphere profile, the velocity distribution has a Maxwell-Boltzmann form.

Astrophysical uncertainties in DD experiments

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Completely unknown. Rely on theoretical considerations  Local dark matter velocity distribution?

▪ Dark matter-only simulations. Show deviations from Maxwell-Boltzmann ▪ Hydrodynamical simulations (DM+baryons). Inconclusive at the moment.

Bozorgnia et al'16

▪ If the density distribution follows a singular isothermal sphere profile, the velocity distribution has a Maxwell-Boltzmann form.

Astrophysical uncertainties in DD experiments

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v f ( v )

AI, Kavanagh, Rappelt’18

Astrophysical uncertainties in DD experiments

Consider “distortions” of the Maxwell-Boltzmann distribution

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v f ( v )

AI, Kavanagh, Rappelt’18

Astrophysical uncertainties in DD experiments

Consider “distortions” of the Maxwell-Boltzmann distribution

C

  • l

l i d e r s

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Some caveats in collider DM searches

Consider an invisible particle decaying into visible particles

  • If short lifetime, the visible particles can be observed at the detector
  • If very long lifetime, the invisible particle leaves the detector, but the

decay products may leave an imprint in BBN, CMB or cosmic rays.

  • A “blind spot” for intermediate lifetimes.

1- The particle produced is invisible, but not necessarily dark matter. (Not cosmologically long-lived? Only a subdominant DM component? But anyway new physics, not discoverable at direct detection experiment.)

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SLIDE 46

Some caveats in collider DM searches

Consider an invisible particle decaying into visible particles

  • If short lifetime, the visible particles can be observed at the detector
  • If very long lifetime, the invisible particle leaves the detector, but the

decay products may leave an imprint in BBN, CMB or cosmic rays.

  • A “blind spot” for intermediate lifetimes.

1- The particle produced is invisible, but not necessarily dark matter. (Not cosmologically long-lived? Only a subdominant DM component? But anyway new physics, not discoverable at direct detection experiment.)

Chou, Curtin, Lubatti’16

Also FASER, CODEX-b...

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Some caveats in collider DM searches

Ideally, the DM parameters may be determined at a collider and used to calculate their abundance. Interplay colliders G cosmology. 1- The particle produced is invisible, but not necessarily dark matter. (Not cosmologically long-lived? Only a subdominant DM component? But anyway new physics, not discoverable at direct detection experiment.)

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Some caveats in collider DM searches

Ideally, the DM parameters may be determined at a collider and used to calculate their abundance. Interplay colliders G cosmology. 1- The particle produced is invisible, but not necessarily dark matter. (Not cosmologically long-lived? Only a subdominant DM component? But anyway new physics, not discoverable at direct detection experiment.)

Baltz et al’06

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SLIDE 49

1- The particle produced is invisible, but not necessarily dark matter. (Not cosmologically long-lived? Only a subdominant DM component? But anyway new physics, not discoverable at direct detection experiment.)

Some caveats in collider DM searches

Ideally, the DM parameters may be determined at a collider and used to calculate their abundance. Interplay colliders G cosmology.

Baltz et al’06

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SLIDE 50

Some caveats in collider DM searches

Ideally, the DM parameters may be determined at a collider and used to calculate their abundance. Interplay colliders G cosmology. 1- The particle produced is invisible, but not necessarily dark matter. (Not cosmologically long-lived? Only a subdominant DM component? But anyway new physics, not discoverable at direct detection experiment.)

Baltz et al’06

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Some caveats in collider DM searches Some caveats in collider DM searches Some caveats in collider DM searches

2- The effective theory approach may be not sufficient or be simply incorrect. (analysis more model dependent, but collider experiments offer extra information about the dark sector couplings/particles).

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Some caveats in collider DM searches Some caveats in collider DM searches Some caveats in collider DM searches

Ma Many p poss ssible ble re reali lizations o s of t the ef effec ective i ive intera eractio ion Ma Many p poss ssible ble re reali lizations o s of t the ef effec ective i ive intera eractio ion

2- The effective theory approach may be not sufficient or be simply incorrect. (analysis more model dependent, but collider experiments offer extra information about the dark sector couplings/particles).

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2- The effective theory approach may be not sufficient or be simply incorrect. (analysis more model dependent, but collider experiments offer extra information about the dark sector couplings/particles).

Some caveats in collider DM searches Some caveats in collider DM searches Some caveats in collider DM searches

Ma Many possibl ssible rea reali lizations s of t the ef e effec ective e in intera eraction Ma Many possibl ssible rea reali lizations s of t the ef e effec ective e in intera eraction

Which dark matter particle? Which mediator (if any)? What is the role of the mediator in the phenomenology?

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2- The effective theory approach may be not sufficient or be simply incorrect. (analysis more model dependent, but collider experiments offer extra information about the dark sector couplings/particles).

Some caveats in collider DM searches Some caveats in collider DM searches Some caveats in collider DM searches

Ma Many possibl ssible rea reali lizations s of t the ef e effec ective e in intera eraction Ma Many possibl ssible rea reali lizations s of t the ef e effec ective e in intera eraction

Which dark matter particle? Which mediator (if any)? What is the role of the mediator in the phenomenology?

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2- The effective theory approach may be not sufficient or be simply incorrect. (analysis more model dependent, but collider experiments offer extra information about the dark sector couplings/particles).

Some caveats in collider DM searches Some caveats in collider DM searches Some caveats in collider DM searches

Ma Many possibl ssible rea reali lizations s of t the ef e effec ective e in intera eraction Ma Many possibl ssible rea reali lizations s of t the ef e effec ective e in intera eraction Three parameters:

  • DM mass, m

c

  • Mediator mass, m

η

  • Coupling constant, y
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2- The effective theory approach may be not sufficient or be simply incorrect. (analysis more model dependent, but collider experiments offer extra information about the dark sector couplings/particles).

Some caveats in collider DM searches Some caveats in collider DM searches Some caveats in collider DM searches

Ma Many possibl ssible rea reali lizations s of t the ef e effec ective e in intera eraction Ma Many possibl ssible rea reali lizations s of t the ef e effec ective e in intera eraction

Fixed by the requirement of reproducing the correct DM abundace. Parameter space of the model spanned by m

cand m η

Three parameters:

  • DM mass, m

c

  • Mediator mass, m

η

  • Coupling constant, y
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For , the interaction can be described by a contact term. For every dark matter mass, there is always a choice of the coupling and the mediator mass that reproduces the observed DM abundance. χ χ fR fR fR fR η χ χ

y y

Majorana DM with t-channel scalar mediator

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For , the interaction can be described by a contact term. For every dark matter mass, there is always a choice of the coupling and the mediator mass that reproduces the observed DM abundance. χ χ fR fR fR fR η χ χ

y y

Majorana DM with t-channel scalar mediator

The phenomenology is completely modified when the mediator is light

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If the mediator and the dark matter have comparable masses, the mediator is present in the thermal plasma during the epoch of freeze-out.

~ y4 ~ y2g2 ~ g4

New channels deplete the number of dark matter particles, via “coannihilations”, and lower the dark matter relic abundance.

Griest, Seckel '91

Majorana DM with t-channel scalar mediator

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If the mediator and the dark matter have comparable masses, the mediator is present in the thermal plasma during the epoch of freeze-out.

~ y4 ~ y2g2 ~ g4

New channels deplete the number of dark matter particles, via “coannihilations”, and lower the dark matter relic abundance.

Griest, Seckel '91

Majorana DM with t-channel scalar mediator

Rate compared to χχDqq suppressed by Rate compared to χχDqq suppressed by

n/s m/T

~ exp(-m/T)

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Majorana DM with t-channel scalar mediator

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Majorana DM with t-channel scalar mediator

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Three different regimes

 .. The scalar mediator cannot be produced at the colliders; only the DM.

The signal consists on a monojet/monophoton/mono-W/Z boson plus missing transverse momentum.

 . The scalar mediator might be produced at the colliders and then

decays into the DM plus a quark/lepton. However, the jets and leptons are too soft to be detected.

q q χ

 . . . The scalar mediator might be produced at the colliders and then decays into the DM plus a quark/lepton. The signal consists of missing transverse momentum plus two jets/two leptons. The signal consists on a monojet/monophoton/mono-W/Z boson plus missing transverse momentum.

e.g e.g χ

Collider signals

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Production of scalar mediators

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Mediated by EW interactions

Production of scalar mediators

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Mediated by the strong interaction

Production of scalar mediators

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Mediated by a Yukawa interaction

Production of scalar mediators

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Production of scalar mediators

DM coupling to uR DM coupling to uR

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Exists only for c Majorana. Cross section enhanced for large mc. Relevant for thermal DM, since y=O(1)

DM coupling to uR DM coupling to uR

Production of scalar mediators

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Limits from colliders Limits from colliders

Garny et al’14

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Garny et al’14

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Garny et al’14

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Various diagrams contribute to the scattering of a dark matter particle with a nucleon:

Interplay with direct detection experiments

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Various diagrams contribute to the scattering of a dark matter particle with a nucleon: The interaction DM-nucleon exists for any

Interplay with direct detection experiments

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Dark matter coupling to leptons. Various diagrams contribute to the scattering of a dark matter particle with a nucleon: The interaction DM-nucleon exists for any

Interplay with direct detection experiments

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Various diagrams contribute to the scattering of a dark matter particle with a nucleon: DM coupling to heavy quarks The interaction DM-nucleon exists for any

Interplay with direct detection experiments

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Various diagrams contribute to the scattering of a dark matter particle with a nucleon: The interaction DM-nucleon exists for any DM coupling to light quarks

Interplay with direct detection experiments

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Tree level: DM coupling to light quarks: spin independent interaction DM coupling to light quarks: spin independent interaction

  • Dim. 8 operator. Singular when
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Tree level: DM coupling to light quarks: spin independent interaction DM coupling to light quarks: spin independent interaction One loop:

  • Dim. 7 operator (but loop suppressed). Regular when
  • Dim. 8 operator. Singular when
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DM coupling to quarks: spin independent interaction DM coupling to quarks: spin independent interaction

Garny et al’14

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DM coupling to quarks: spin dependent interaction DM coupling to quarks: spin dependent interaction Tree level:

  • Dim. 6 operator. Singular when
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Garny et al’14

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Impact for dark matter produced via thermal freeze-out

Interplay with direct detection experiments

Garny et al’14

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Impact for dark matter produced via thermal freeze-out

Interplay with direct detection experiments

Garny et al’14

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Interplay with direct detection experiments

Scalar dark matter with fermion mediator

Giacchino et al’15

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Collider searches vs. direct detection

 Very fast progress in direct detection experiments.

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Collider searches vs. direct detection

 Very fast progress in direct detection experiments.

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SLIDE 88

Collider searches vs. direct detection

 Very fast progress in direct detection experiments.

LZ coll. IDM’18

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Collider searches vs. direct detection

 Very fast progress in direct detection experiments. “A first science run could start by 2023”

“DARWIN: towards the ultimate dark matter detector”, arXiv:1606.07001

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Collider searches vs. direct detection

 Very fast progress in direct detection experiments. Not so fast in collider searches...

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Collider searches vs. direct detection

 Yet, collider experiments are an invaluable tool probe WIMP dark matter (and new physics in general)

1) The data are available for analysis.

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SLIDE 92

Collider searches vs. direct detection

 Yet, collider experiments are an invaluable tool probe WIMP dark matter (and new physics in general)

1) The data are available for analysis. 2) The energy and luminosity of the collider are known (no astrophysical uncertainties)

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SLIDE 93

Collider searches vs. direct detection

 Yet, collider experiments are an invaluable tool probe WIMP dark matter (and new physics in general)

1) The data are available for analysis. 2) The energy and luminosity of the collider are known (no astrophysical uncertainties) 3) May provide information about the dark sector (mediators, couplings…). The DM abundance could (in principle) be reconstructed, providing a test of WIMP production

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SLIDE 94

Collider searches vs. direct detection

 Yet, collider experiments are an invaluable tool probe WIMP dark matter (and new physics in general)

1) The data are available for analysis. 2) The energy and luminosity of the collider are known (no astrophysical uncertainties) 3) May provide information about the dark sector (mediators, couplings…). The DM abundance could (in principle) be reconstructed, providing a test of WIMP production. 4) In some scenarios, collider searches probe regions of the parameter space difficult to probe with direct detection (or indirect detection) experiments. Also, they can test possible signals in other experiments.

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Collider searches vs. direct detection

5) Collider experiments provide the best sensitivity to light WIMPs...

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SLIDE 96

Collider searches vs. direct detection

5) Collider experiments provide the best sensitivity to light WIMPs... 6) … and in some scenarios, even better sensitivity than the “ultimate” dark matter detectors.

arXiv:1606.07001

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Collider searches vs. direct detection

5) Collider experiments provide the best sensitivity to light WIMPs... 6) … and in some scenarios, even better sensitivity than the “ultimate” dark matter detectors. 7) … even reaching beyond the “neutrino floor”

arXiv:1606.07001

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FIMP IMPs at s at col colli liders ers

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SLIDE 99

Feebly interacting massive particles have very weak couplings to the Standard Model particles and were always out of thermal equilibrium. Yet, they are produced via scatterings/decays in the primeval plasma.

(e.g. h→ χχ, or η+→ l+χ). Very slow processes due to the small coupling.

The freeze-in mechanism

Their number density can only increase, until the plasma is too diluted to allow collisions

  • r the mother particles have

disappeared

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SLIDE 100

Searching for FIMP dark matter at the LHC

Consider a FIMP that is produced via decays of a charged scalar particle. → Long-lived charged particle.

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SLIDE 101

Searching for FIMP dark matter at the LHC

Consider a FIMP that is produced via decays of a charged scalar particle. A fraction of the charged scalars gets trapped in the detector, and decays at late times.

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SLIDE 102

Conclusions

 Dark matter in the form of Weakly Interacting Massive Particles is among the best motivated scenarios for Physics beyond the Standard Model. Bonus: it is testable, now, in various ways.  The LHC is complementary in many ways to direct and indirect WIMP searches. It’s free of astrophysics uncertainties and may provide deeper insights on the dark sector.  Moreover, in some scenarios the LHC constitutes the best probe to WIMP dark matter (e.g. light WIMPs). High discovery potential. The role of colliders will increase if direct detection experiments reach the neutrino floor without observing signals.  The LHC can also probe non-WIMP dark matter scenarios, e.g. FIMPs.