comparing a ccelerator and direct dark matter searches

Comparing Accelerator and direct Dark Matter

searches

G. Azuelos24 Jul 2014 Dark Matter workshop - Montreal 1

WIMPS: what can we say about their

properties? possible origins? many models

What is an effective theory? Detecting DM from missing

momentum at colliders: LEP, Tevatron, LHC

Validity of effective theory

Some references:• Bai, Fox and Harnik, 1005.3797v2• P. Fox et al., 1103.0240• J. Goodman et al., 1008.1783, 1111.2359• G. Busoni et al., 1307.2253, 1402.1275• O. Buchmueller et al., 1308.6799• M. Papucci et al., 1402.2285• KICP workshop 2013:

https://kicp-workshops.uchicago.edu/DM-LHC2013/presentations.php

In early universe, WIMPS are in thermal equilibrium and annihilate until the density is too low freeze-out

Some possibilities: LSP: neutralinos, gravitinos LKP: Kaluza-Klein state in Universal Extra dimensions LTP: Little Higgs with T parity also, in Technicolor, composite Higgs models Higgs portal Z’ portal fermion portal useful to have a model-independent approach

In collider experiments: non-interacting, invisible particles missing ET

Properties of WIMPS

24 Jul 2014 Dark Matter workshop - Montreal 2

Effective theories

Assume new physics at some high energy scale L Energy scale at which measurement is performed: Q

Observed effect of new physics is small and needs to be calculated at 1st order only


W

Classic example: Fermi theory: Weak interaction is well approximated, in nuclear physics, by a contact interaction, when, in fact, it is an exchange of a heavy particle

Propagator of the heavy particle:

valid as long as

Effective approximation


(weak contact coupling)

(f = scalar mediator)

Mq

q

c

c

Translate to Direct Detection


Mq

q

c

ctime

Different kinematics


Assuming weak interactions (neutralinos):

spin-independent:

spin-dependent

Wimps interacting with matter


c c

q q

Z

cc

qq

c c

q q

h,H

c

cq

q

spin-dependent cross sections

proton neutron


arX

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3797

v2B

ai,

Fo

x an

d H

arn

ik

at Tevatron

Light mediator


momentum and spin-dependent model

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3797

v2B

ai,

Fo

x an

d H

arn

ik

LEP shines light on Dark Matter

4 effective operators


• single photon• cm energy ~ 200 GeV• central: 45o < q < 135o

• forward: 12o < q < 32o

• v. forward: 3.8o < q < 8o

simulated conditions, accounting for efficiencies as function of angle and resolutions

arX

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0240

v1P.

Fo

x et

al.

DM nucleon scattering cross section

strong constraints on spin-dependent at low mass: no A2 dependence

also considered… if lepton coupling only limits on annihilation lighter mediator effects


arX

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0240

v1P.

Fo

x et

al.

Operators

DiracComplex scalarsReal scalars

Many curves obtained

for the limits on L and for limits derived on nucleon cross sections for the different operators


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1783

v2J.

Go

od

man

et

al.

reach at colliders, in EFT


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v2J.

Go

od

man

et

al.

spin-independent

spin-dependent

LHC


ATLAS 1210.4391

Validity condition of EFT


Definition: ; Typically expect

• condition for perturbativity:

• mediator heavier than WIMP:

• truncation of propagator expansion:

• s-channel:

arX

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2253

G.

Bu

son

i et

al.

The lower Q, the better the EFT approximation

Momentum transfer Q


p1

p2

p3

p4

k

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307.

2253

G.

Bu

son

i et

al.

RL


Fraction of cross section for which Q < L :

for scalar operator:

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2253

G.

Bu

son

i et

al.

RL


for scalar operator:

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2253

G.

Bu

son

i et

al.

Compared to ATLAS


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1275

G.

Bu

son

i et

al.

rUV/eff


Ratio of cross sections obtained with UV completed theory (s-channel scalar mediator) and with EFT :

The smallet pT and mc are, the better the EFT approximation.

arX

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2253

G.

Bu

son

i et

al.

Beyond Effective Field Theory at the LHC


O. B

uch

mu

elle

r et

al.,

arX

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6799

• EFT is valid if

• cross section enhanced if mediator is on-shell, for example

• Consider CMS monojet analysis, as basis (7 and 8 TeV analyses)

• Use Monte Carlo (MCFM 6.6) to simulate dark matter monojet process

• includes full effects of mediator propagator and width, in s-channel

• consider axial-vector and vector operators only:

• apply CMS cuts

• one hard jet: pT > 100 GeV

• signal regions (best of their signal regions)

• parton level cuts, with geometric acceptance

• background simulated with MadGraph:

• pythia showering and PGS detector simulation

• compared results with CMS to validate their MC analysis

Simplified model


s-channel axial-vector interaction: applies also to Majorana DM, and more interesting spin-dependent limits

EFT valid if M >> Q• Q > 500 GeV when pT(j) > 100 GeV, Etmiss > 400 GeV• find condition: M > 2.5 TeV

EFT OK

within 20%

resonant

production

of mediator

EFT OK

resonant production of mediator

2.5 TeV

Region 1: Very high mediator mass: EFT OK


O. B

uch

mu

elle

r et

al.,

arX

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6799

Region II : resonant enhancement


• On-shell production of mediator if

• production enhanced EFT limit conservative

Limit on L scales as ~ G-1/4 at the resonance peak

Region III for CMS conditions

Region II for CMS conditions

see also Goodman & Shepherd, arXiv:1111.2359

O. B

uch

mu

elle

r et

al.,

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6799

CMS EXO-12-048 PAS

https://twiki.cern.ch/twiki/bin/view/CMSPublic/PhysicsResultsEXO12048


Region III: very light mediator – EFT limit too strong


• In the limit where the mediator is very light, • the cross section does not depend on its mass since

• EFT assumes M is very large (and g small for the same L)

O. B

uch

mu

elle

r et

al.,

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6799

Comparison to Direct Detection


O. B

uch

mu

elle

r et

al.,

arX

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6799

Recommendations and Conclusion


Validity of EFT depends a lot on the assumptions and parameters:• 4 parameters:• small dependence on width G in resonance region• LHC should provide limits on L in M-mc plane (in s-channel assumption?)

• for few values of G/M

Complementarity:M. Cahill-Rowley, 1305.6921

EXTRAS


tree level coupling to leptons only


Assume coupling to leptons only


Limits on Λ


Upper limits on annihilation cross sections


Annihilation cross section, compared to astronomical limits

LEP limits better than Fermi for low masses


With different mediator masses

strong dependence on width, if M > 2 mwimp, since it is produced on-shell


Wimp-Nucleus cross section


Annihilation cross section


Limits on L

monojet limits from CDF• ET(jet) > 80 GeV• Etmiss > 80 GeV• 2nd jet ET < 30 GeV• no add. jet with ET > 20 GeV


Bai, Fox and Harnik,arXiv:1005.3797

need quark content of nucleon

spin-independent cross section

very sensitive at low massestests also couplings to higher generations

proton


Bai, Fox and Harnik,arXiv:1005.3797


c c

q q

h,H

c

cq

q c c

q q

Z

cc

qq

http://www.worldscientific.com/doi/abs/10.1142/S0218301392000023?queryID=%24%7BresultBean.queryID%7D


ATLAS 1210.4391


ATLAS mono-Z1404.0051


CMSEXO-12-048 PAS



Bai, at DM workshop 2013



comparing a ccelerator and direct dark matter searches

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