Summary of WG3 Thursday Parallel Session

Bertrand Echenard and Eder Izaguirre

Accelerator-Based Searches

If discovery A path towards a Lagrangian

Mediator physics (coupling strengths, mass scale,

separately coupling to leptons, quarks)

Dark Matter coupling strength to mediator

Sensitivity to multiple thermal DM scenarios (scalar DM, majorana, pseudo-dirac)

If Null Result Robust statement about light thermal DM scenarios

Offer a robust program to go after light thermal DM targets

Sensitive to large class of thermal DM target scenarios

HPseudoLDirac FermionInelastic Scalar

Majorana Fermion

Elastic Scalar

1 10 102 10310-55.

10-53.

10-51.

10-49.

10-47.

10-45.

10-43.

10-41.

10-39.

10-37.

10-35.

mDMHMeVL

seHcm

2 L

current

MeV-GeV Thermal

A’-tree

A’-

From P. Schuster’s talk

Accelerator-Based Searches

Pseudo-D

irac Fermi

on Relic T

arget

Majorana

RelicTarg

et

Elastic &

Inelastic S

calarRelic

Targets

BaBar

LHC

LEP

NA64

Belle IIE137

MiniBooNE

LSND

Pseudo-D

irac Fermi

on Relic T

arget

Majorana

RelicTarg

et

Elastic &

Inelastic S

calarRelic

Targets

1 10 102 10310-1610-1510-1410-1310-1210-1110-1010-910-810-710-610-510-4

mc @MeVD

y=e2aDHm cêm A

'L4

Thermal Relic Targets & Current Constraints

Current Landscape

Direct access to mediator physics

From O. Moreno’s talk

✔ ≈ →

✔

→ →

Toy MC

Current Landscape

Proton Beam-dump approach

From R. Cooper’s talk

New Mexico State University

All About Discovery!nmsu.edu

Confidence Limit Results• Many ways to

“slice” parameter space

• This parameter choice is rejected as solution for g-2anomaly (Vector Portal)

3/23/17 R.L. Cooper - U.S. Cosmic Visions 25

(GeV)χm2−10 1−10 1

4 ) V/m χ

'(mα2 ε

Y =

11−10

10−10

9−10

8−10

7−10

LSND

E137

BaBar

BaBar2017

+invis.+π→+K

NA64

invis.→ψJ/

NucleonDetectionDirect

ElectronDetectionDirect

Relic Density

favoredµα

' = 0.5α, χ = 3mVmMB 90% CLMB 90% Sensitivity90% Sensitivity Steel

σ 1 ±σ 2 ±

Dark Matter Search in a Proton Beam Dump with MiniBooNE

A.A. Aguilar-Arevalo,1 M. Backfish,2 A. Bashyal,3 B. Batell,4 B.C. Brown,2 R. Carr,5 A. Chatterjee,3

R.L. Cooper,6, 7 P. deNiverville,8 R. Dharmapalan,9 Z. Djurcic,9 R. Ford,2 F.G. Garcia,2 G.T. Garvey,10

J. Grange,9, 11 J.A. Green,10 W. Huelsnitz,10 I.L. de Icaza Astiz,1 G. Karagiorgi,5 T. Katori,12 W. Ketchum,10

T. Kobilarcik,2 Q. Liu,10 W.C. Louis,10 W. Marsh,2 C.D. Moore,2 G.B. Mills,10 J. Mirabal,10 P. Nienaber,13

Z. Pavlovic,10 D. Perevalov,2 H. Ray,11 B.P. Roe,14 M.H. Shaevitz,5 S. Shahsavarani,3 I. Stancu,15

R. Tayloe,6 C. Taylor,10 R.T. Thornton,6 R. Van de Water,10 W. Wester,2 D.H. White,10 and J. Yu3

1Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Mexico City 04510, Mexico2Fermi National Accelerator Laboratory, Batavia, IL 60510

3University of Texas (Arlington), Arlington, TX 760194University of Pittsburgh, Pittsburgh, PA 15260, USA

5Columbia University; New York, NY 100276Indiana University, Bloomington, IN 47405

7New Mexico State University, Las Cruces, NM 880038Center for Theoretical Physics of the Universe, Institute for Basic Science (IBS), Daejeon, 34051, Korea

9Argonne National Laboratory, Argonne, IL 6043910Los Alamos National Laboratory, Los Alamos, NM 87545

11University of Florida, Gainesville, FL 3261112Queen Mary University of London, London, E1 4NS, UK

13Saint Mary’s University of Minnesota, Winona, MN 5598714University of Michigan, Ann Arbor, MI 4811115University of Alabama, Tuscaloosa, AL 35487

(Dated: February 10, 2017)

The MiniBooNE-DM collaboration searched for vector-boson mediated production of dark matterusing the Fermilab 8 GeV Booster proton beam in a dedicated run with 1.86⇥1020 protons deliveredto a steel beam dump. The MiniBooNE detector, 490 m downstream, is sensitive to dark mattervia elastic scattering with nucleons in the detector mineral oil. Analysis methods developed forprevious MiniBooNE scattering results were employed, and several constraining data sets weresimultaneously analyzed to minimize systematic errors from neutrino flux and interaction rates. Noexcess of events over background was observed, leading to an 90% confidence limit on the dark-matter cross section parameter, Y = ✏2↵0(m�/mv)

4 . 10�8, for ↵0 = 0.5 and for dark-mattermasses of 0.01 < m� < 0.3 GeV in a vector portal model of dark matter. This is the best limit froma dedicated proton beam dump search in this mass and coupling range and extends below the massrange of direct dark matter searches. These results demonstrate a novel and powerful approach todark matter searches with beam dump experiments.

PACS numbers: 95.35.+d,13.15.+g

Introduction — There is strong evidence for dark mat-ter (DM) from observations of gravitational phenomenaacross a wide range of distance scales [1]. A substantialprogram of experiments has evolved over the last sev-eral decades to search for non-gravitational interactionsof DM, with yet no undisputed evidence in this sector.Most of these experiments target DM with weak scalemasses and are less sensitive to DM with masses below afew GeV. To complement these approaches, new searchstrategies sensitive to DM with smaller masses should beconsidered [2].

Fixed-target experiments using beams of protons orelectrons can expand the sensitivity to sub-GeV DM thatcouples to ordinary matter via a light mediator parti-cle [3–18]. In these experiments, DM particles may beproduced in collisions with nuclei in the fixed target, of-ten a beam dump, and may be identified through interac-tions with nuclei in a downstream detector. Results frompast beam dump experiments have been reanalyzed to

Be

Target

Earth

Air

Decay Pipe

Steel

Beam Dump

MiniBooNE Detector

p⇡0

V

�

�†

�N

�50m 4m 487m

FIG. 1. Schematic illustration of this DM search using thethe Fermilab BNB in o↵-target mode together with the Mini-BooNE detector. The proton beam is steered above the beryl-lium target in o↵-target mode lowering the neutrino flux.

place limits on the parameters within this class of models.In this Letter, we report on the first dedicated search ofthis type (proposed in [6]), which employs 8 GeV protonsfrom the Fermilab Booster Neutrino Beam (BNB), re-configured to reduce neutrino-induced backgrounds, com-bined with the downstream MiniBooNE (MB) neutrinodetector (Fig. 1).

arX

iv:1

702.

0268

8v1

[hep

-ex]

9 F

eb 2

017

deNiverville, Pospelov, Ritz 1107.4580

1. (quasi)elastic scattering 3

10

Beam

p �!Target Detector

�i

�

A��0, �

�1

�2

A�

�i �j

T T

�1�

2

f�f+A�and/or

Beam

e/p �!Target/Dump Detector

�i

A�

Z

e/p

e/p

�1

�2

p

Z

�

A��0, � �1

�2

A�

�i �j

T T

and/or

�1�

2

f�f+A�

FIG. 2. Inelastic DM production at electron and proton beam dump experiments via dark bremsstrahlung and meson decay. The resulting�1, �2 pair can give rise to a number of possible signatures in the detector: �2 can decay inside the fiducial volume to deposit electromagneticenergy; both �1 and �2 can scatter off detector targets T and impart visible recoil energies to these particles; or �1 can upscatter into �2,which can then decay promptly inside the detector to deposit a visible signal.

7

e� �!

ECAL/HCAL

TargetTracker

e�

�1�2

Invisible

e� �!

Active Target (ECAL/HCAL)

e�

�1�2

Invisible

A�

Z

e�

e�

�1

�2

FIG. 3. Inelastic DM production at electron beam fixed-target missing energy/momentum experiments. Left: Setup for an LDMX stylemissing momentum experiment [2, 18] in which a (⇠ few GeV) beam electron produces DM in a thin target (⌧ radiation length) and therebyloses a large fraction of its incident energy. The emerging lower energy electron passes through tracker material and registers as a signal eventif there is no additional energy deposited in the ECAL/HCAL system downstream, which serves primarily to veto SM activity. Right: Setupfor an NA64 style experiment in which the beam (typically at higher energies, ⇠ 30 GeV) produces the DM system by interacting with aninstrumented, active target volume [19]. As with LDMX, the instrumented region serves to verify that the beam electron has abruptly lost mostof its energy and that there is no additional SM activity downstream.

for vector, scalar, and fermionic mediators, respectively.However, coupling a fermionic mediator to the lepton por-tal requires additional model building1 and scalar mediators,which mix with the Higgs are ruled out for predictive mod-els in which DM annihilates directly to SM final states (seeSec. II C and [26] for a discussion of this issue), so we restrict

1 A fermionic mediator coupled to the lepton portal requires additionalmodel building to simultaneously achieve a thermal contact through thisinteraction and yield viable neutrino textures; the coupling to the mediatormust be suppressed by neutrino masses, so it is generically difficult for theinteraction rate to exceed Hubble expansion.

our attention to abelian vector mediators; a nonabelian fieldstrength is not gauge invariant, so kinetic mixing is forbidden.

Alternatively, the mediator could couple directly to SMparticles if both dark and visible matter are charged underthe same gauge group. In the absence of additional fields,anomaly cancellation restricts the possible choices to be

U(1)

B�L

, U(1)

`

i

�`

j

, U(1)

3B�`

i

, (2)

and linear combinations thereof. In most contexts, the rele-vant phenomenology in fixed-target searches is qualitativelysimilar to the vector portal scenario, so below we will ignorethese possibilities without loss of essential generality. Wenote, however, that viable models for both protophobic [27]

��

Signatures @ Proton Beam Dumps

6

a)A0

· · ·

Z

e�

e�

'`

'⇤h

b) · · ·

'`

A0⇤

e�

e+

A0

'` 'h

p, n, e� ER

FIG. 6: a) Scalar DM pair production from electron-beam col-lisions. An on-shell A0 is radiated and decays o↵ diagonally to'h,` pairs. b) Inelastic up scattering of the lighter '` into theheavier state via A0 exchange. For order-one (or larger) masssplittings, the metastable state promptly de-excites inside thedetector via 'h ! '`e

+e�. The signal of interest is involvesa recoiling target with energy ER and two charged tracks toyield a instinctive, zero background signature.

a)A0

Z

e�

e�

�1

�2

�1

�2

A0e+

e�

A0

�1

�2

Z, p, n, e�

�1

A0

�2

e�

e+

FIG. 7: a) Scalar DM pair production in electron-nucleus col-lisions. An on-shell A0 is radiated and decays o↵ diagonally to'h,` pairs. b) Inelastic up scattering of the lighter '` into theheavier state via A0 exchange inside the detector. For order-one (or larger) mass splittings, the metastable state promptlyde-excites inside the detector via 'h ! '`e

+e�. This processyields a target (nucleus, nucleon, or electron) recoil ER andtwo charged tracks, which is a instinctive, zero backgroundsignature, so nuclear recoil cuts need not be limiting.

� �

Batell, Pospelov, Ritz 0903.0363

Coloma, Dobrescu, Frugiuele, Harnik 1512.03852

@ LSND,MiniBooNE, T2K, NOvA, DUNE…

Batell, deNiverville, McKeen, Pospelov, Ritz 1405.7049

Frugiuele 1701.05464

Can explore/testScalar

Majoranapseudo-Dirac DM

32

⇠ ✏4↵D

Current Landscape

July 2016 results

• No event observed in the signal box from the July’2016 data.

• New limits set on the !-A’

mixing strength.arXiV:1610.02988

Phys. Rev. Lett. 118, 011802 (2017)

From D. Benarjee’s talk

ECAL

HCALA’e- beam

NA64 —> fixed target experiment combining the active beam dump technique with missing energy measurement searching for invisible decays of massive A’ produced in the reaction eZ—> eZA’ of electrons scattering off a nuclei (A,Z), with a mixing strength 10-6 < ! < 10-3 and masses MA’ ~ sub-GeV range.

100 GeV electrons dumped against an ECAL, a sandwich of lead and scintillators (34 X0), to produce massive A’ through scattering with the heavy nuclei.

The typical signature for a signal will be missing energy in the ECAL and no activity in the the VETO and HCAL.

Background from hadrons, muons and low energy electrons must be rejected upstream.

!

!

Missing momentumtracker/SR tagging

Selection of 100 GeV electrons VETO

NA64: Search for dark sector physics in missing energy events

⇠ ✏2

Missing energy

Current Landscape

From C. Hearty’s talk

(GeV) A'm2−10 1−10 1 10

ε

4−10

3−10

2−10

BaBar 2017

E787, E949

NA64

σ 2±µ

(g-2)

α vs e(g-2)

-1Belle II projection 20 fb

Projected Belle II exclusion region, 20 fb-1

• Assumes we can quantitatively predict background levels.- photon efficiency over barrel/endcap gaps.

15

better calorimeter hermeticity to suppress e+e- → γ γ

Reach masses of 9.1–9.5 GeV/c2 with lower trigger threshold (vs 8 GeV/c2 for BaBar)

C. Hearty | Dark sector at BaBar, Belle, and Belle II | US Cosmic Visions

BaBar single photon search

• Optimized for and interpreted in terms of a dark photon A′ decaying invisibly.

• We assume on-shell A′ (mχ < mA′/2), so signal is a monoenergetic photon.

• analysis is otherwise not sensitive to mχ or to the coupling of the χ to the A′.

3

E⇤� =

ps

2� m2

A0

2ps

C. Hearty | Dark sector at BaBar, Belle, and Belle II | US Cosmic Visions

⇠ ✏2

Can also do dark spectroscopy e.g. dark higgs

Discussed New Theoretical Ideas

Potential new muon beam-dump experiments (Y. Zhong)

Short-baseline neutrino facilities sensitivity to leptophobic mediators (C. Frugiuele)

6-quark ~ 1.5 GeV DM candidate (G. Farrar)

Complementarity talk on Be^8 anomaly theory implications (I. Gahlon)

Non-Abelian DS at Fixed-Targets (N. Blinov)

Today

New proposals!