Report from the PAAPParticle Astrophysics Advisory Panel

Philip Mauskopf, Cardiff University

Giles Hammond, University of GlasgowAlex Murphy: University of EdinburghPhilip Harris: University of SussexJim Hinton: University of LeedsSilvia Pascoli: Durham UniversityDeborah Miller, Dave Godfrey: STFC

https://paap.astro.cf.ac.uk/doku.php

Particle Astrophysics The field of particle astrophysics encompasses projects measuring and

characterising the properties of particles and radiation from space apart from standard electromagnetic radiation. These projects often lie at the intersection between Cosmology, Astrophysics and Nuclear and Particle physics.

Internationally, particle astrophysics is defined by technique

Two ways to measure particles from space:

Direct detection - Gravity wave telescopes, Neutrino detectors and telescopes, Cosmic ray telescopes, Gamma ray telescopes, Dark matter detectors and telescopes, Other exotic particle searches – e.g. axions, magnetic monopoles, etc.

Indirect detection – pulsar timing, CMB, weak lensing, LSS, etc.

Thus there is an overlap between the activities of PAAP and FUAP / PPAP / NPAP (science and technology overlap)

Particle Astrophysics: The European Strategy There are 2 reviews which we feel are relevant to UK strategy;

2008 STFC programmatic review (http://www.stfc.ac.uk/resources/pdf/FinalProgRevOutcome.pdf)

ASPERA (http://www.aspera-eu.org)

ASPERA – is a network of national government agencies responsible for coordinating and funding national research efforts in Particle Astrophysics

– has identified the development of a roadmap for Particle Astrophysics in Europe as one of its main deliverables

ASPERA Magnificent Seven (Sep 2008)

• A ton-scale detectors for dark matter search

• A ton-scale detector for the determination of the fundamental nature and mass of neutrinos

• A megaton-scale detector for the search for proton decay, for neutrino astrophysics and for the investigation of neutrino properties

• A large array of Cherenkov Telescopes for detection of cosmic high energy gamma-rays

• A cubic kilometre-scale neutrino telescope in the Mediterranean Sea

• A large array for the detection of charged cosmic rays

• A third-generation underground gravitational antenna

ASPERA – European review of particle astrophysics

ASPERA – European review of particle astrophysics

Fraction of total research budget going to PA by country

STFC yearly PA budget is ~ 6-8 M£

Lowest per capita in EU

Community ConsultationPAAP Community Questionnaire

A community consultation questionnaire was made public on June 9th at the APP in Edinburgh The questions addressed the following;

Part I: A list of projects, compiled by panel members, were given, and the community was asked to add missing projects and state areas of research which were absolutely necessary and why?

Part II: Particle Astrophysics is an area where small projects can have a large impact. The community was asked what typical budget should be allocated to these projects?

Part III: What are the UK areas of strength in particle astrophysics theory and what is needed to maintain and strengthen these areas?

Part IV: What are the key technologies for the future, what are the areas of application and time scales for development? What is the potential economic/industrial impact of these technologies.

Part V: Outreach activities and public engagement?

Part VI: Anything else?

Community ConsultationPAAP Community Questionnaire

Responses were received until 31st July. These were both in the form of individual responses and coordinated responses from a field. The final statistics;

21 UK institutions 47 responses on behalf of 147 researchers. The committee then individually summarised the responses and met

several times to discuss their findings.

Executive Summary

The UK has a high visibility and leadership in several areas of Particle Astrophysics with extremely strong pedigree both experimentally and theoretically.

There were certain clear areas/projects which received high levels of support.

Outreach is particularly active in the field.

Big Questions in Particle Astrophysics

Cosmology and early universe:- What is dark energy and how has it affected the expansion history of the universe?- What is the origin and what are the properties of primordial fluctuations in the early uni-

verse? What is the imprint of these fluctuations on stochastic backgrounds (e.g. CMB,Gravity waves, neutrinos)?

- What happened in the first 3 picominutes? How did the universe take on the propertiesit has today? Are there topological defects? What happened during GUT symmetrybreaking (Was there a GUT symmetry breaking)?

- Why is the universe flat? Inflation? If so, what caused inflation; at what energy scaledid it happen? Does general relativity break down at large scales?

Fundamental particle physics:- What is the nature of dark matter?- Do protons have a finite lifetime?- Does general relativity break down at small scales/high energies? What is the quan-

tum nature of gravity?- What is the nature of fundamental particle interactions at extremely high energies

(higher than particle accelerators can reach)?- What are the properties of neutrinos (e.g. masses, mixing angles, Majorana nature)?- Are there any particles present in the universe which we have not yet detected either

directly or indirectly (e.g. axions, magnetic monopoles, inflaton, etc.)?

High energy universe / Non-thermal universe:- How and where are particles accelerated to ultra-relativistic energies in our galaxy?- What is the origin of the highest energy > EeV cosmic rays?- What is the role of ultra-relativistic particles in active galaxies and in AGN/cluster feed-

back?- What are the properties of black holes?- What happens when black holes or neutron stars collide?- What happens during a supernova?- Are there stable states of matter at densities beyond neutron degeneracy?

Main findingsPrioritisation Document to PPAN

We generally followed the PPAN guidelines while writing the document:

1. Introduction

2. Current Programme and UK Expertise

3. Future Opportunities

4.Technology and Outreach

• The techniques used in Particle Astrophysics can be divided into the following broad areas (with examples of projects that have received UK support indicated in brackets):

• Particle astrophysics theory (cosmology, DM, GW’s, neutrino’s and particle accel.)• Gamma ray astronomy (CTA, HESS, VERITAS)• Direct dark matter detection (EURECA, LUX-ZEPLIN, DRIFT, ArDM)• Gravitational wave detection (LIGO, Advanced-LIGO, LISA)• Neutrinos (SNO+, LAGUNA)• Cosmic rays (AUGER South, ANITA, ACORNE)• CMB polarisation studies (PLANCK, CLOVER)

Main findingsOverlaps with other panels

• Particle astrophysics theory – PPAP and FUAP• Gamma ray astronomy - FUAP (could fall through cracks)• Direct dark matter detection - PPAP, NPAP• Gravitational wave detection - FUAP• Neutrinos - PPAP• Cosmic rays • CMB polarisation studies - FUAP

Main findingsGamma Ray Astronomy

Science areas:Fundamental physics:Lorentz invariance – quantum gravityDark matter annihilation signature

High energy universe (extragalactic):Gamma ray burstsEmission from AGNStarburst galaxies (NGC253 – September 24, 2009)

High energy universe (galactic):BinariesPulsar wind nebulaeGamma ray pulsars

Main findings

Main findingsGamma Ray Astronomy

Science areas:

Main findingsGamma Ray Astronomy

It is essential that the UK maintain a key role in the next generation ground-based gamma ray facility: CTA

CTA is the successor to the current arrays of imaging atmospheric Cherenkov telescopes (IACTs), such as HESS and VERITAS, which over the last decade have helped revolutionise our understanding of many of the highest energy phenomena in the Universe.

Direct Dark Matter SearchesAll the astronomical data consistently point to the existence of dark matter

Lightest supersymmetric particle forms a very good WIMP candidate

Direct Dark Matter Searches

Current limits and projected sensitivities

Main findingsDirect Dark Matter Searches

It is essential that the UK maintain a key role in the next generation dark matter searches

LUX-ZEPLIN is the successor to the current ZEPLIN experiment led by the UK and EURECA is the successor to the current CRESST and EDELWEISS experiments with UK spokesperson. DRIFT and ArDM are important for future dark matter characterisation experiments.

Main findingsGravitational Waves

Science areas:Fundamental physics:Extreme gravity - quantum gravity

Cosmology:Early universe phase transitionsHistory of acceleration

High energy universe:Gamma ray burstsBlack holesSupernovaeBinary mergers

High energy universe:Pulsar glitchesMagnetar flares

Other:Helioseismology

Gravitational WavesCrab Pulsar

• observed luminosity of the Crab nebula accounts for < 1/2 spin down power • spin down due to: electromagnetic braking/particle acceleration/GW emission?• LIGO s5 result:

- ellipticity upper limit: ε < 2.1 x 10-4

- GW energy upper limit < 6% of radiated energy is in GWs

Abbott, et al., “Beating the spin-down limit on gravitational wave emission from the Crab pulsar,” Ap. J. Lett. 683, L45-L49, (2008).

GRB 070201• GRB observed in direction of M31 during s5 science run

• Binary merger in M31 scenario excluded at >99% level

• Cannot exclude an SGR in M31.

Abbott, et al. “Implications for the Origin of GRB 070201 from LIGO Observations”, Ap. J., 681:1419–1430 (2008).

90%

75%50%

25%

Inspiral Exclusion Zone

99%

(1<m1<3 Msun)

The Stochastic GW Background: Beating BBN!

• An isotropic stochastic GW background could come from: - the primordial universe (inflation) - an incoherent sum of point emitters isotropically distributed over the sky• Preliminary LIGO s5/VSR1 result: Ω0, LIGO < 9.0 x 10-6

Main findingsGravitational waves

It is essential that the UK maintain a key role in the next generation gravity wave experiments

The two main future projects are Advanced LIGO and LISApf/LISA

Main findingsNeutrino AstronomyScience areas:Cosmology:Supernova backgroundCosmological neutrinos

High Energy Universe:Emission from AGNGZK neutrinosSupernovae

Other:Solar physicsGeophysics/Atmospheric

Fundamental particles:Neutrino mixing angles Neutrino mass hierarchyCP violation

Main findingsNeutrino Astronomy

So far: Limited to Solar, SN1987A, terrestrial

Main findingsNeutrinos

It is essential that the UK maintain a key role in the next generation neutrino experiments

Neutrinoless double beta decay: Covered by PPAP. SNO+ offers solar/terrestrial detection capability

Priorities:

1. Large scale neutrino detector: R&D for a future large scale neutrino detector for atmospheric, terrestrial, solar and astrophysical neutrinos is essential. Current work is organised within Europe through LAGUNA.

2. Small/Intermediate scale neutrino detector (e.g. SNO+, KM3Net)

Main findingsCosmic Rays

It is essential that the UK maintain scientific leadership in Auger South and pursue R&D for future high energy cosmic ray detectors

Priorities:

1. Auger South construction is completed and has begun science operations. These are expected to last > 10 years. The UK has a leading role in science from Auger.

2. GZK neutrino experiments (ANITA, ARA, ACORNE, LOFAR, SKA)

3. It is not recommended that the UK participate in the next generation cosmic ray facility: Auger North

Main findingsCMB polarisation

Detection of the imprint of gravitational waves on the CMB polarisation would give unique information on the initial seeds of structure in the universe.

This experiment uses the entire universe as a gravitational wave detector. Detection of a stochastic GW background would have high impact

Main findingsCMB polarisation

It is essential that the UK maintain scientific and technical leadership in CMB polarisation experiments

Priorities:

1. Highest priority is participation in PLANCK science

2.Next highest priority is to make use of the investment in CLOVER to make a world-leading measurement and/or participate in other international collaborations (e.g. EBEX, QUITE, SPIDER, QUIJOTE, etc.)

Main findingsPAAP Prioritisation Given the fact that individual grant applications and SOI’s were not available we decided not to explicitly prioritise projects. Instead, the approach we have taken is to highlight to PPAN areas under the criteria of Breadth, Risk Level, Impact, UK Strength and Cost

We recommend supporting a portfolio of facilities in particle astrophysics that balances scientific breadth, impact, UK strength and cost and includes strong support for theory and exploitation of facilities. The table below gives our prioritisation of the different areas in each of these categories.

Area Breadth Risk level Impact level UK strength CostGamma rays Medium Low Medium/High Medium LowCosmic Rays Low/Medium Low Medium Medium/High LowCMB-Pol Low High High High MediumDark Matter Low High High High MediumGravity Waves Medium/High Medium High High HighNeutrinodetectors

Medium/High Medium Medium/High Medium/High Medium

Future OpportunitiesWe fell that participation in R&D, construction and scienceactivities for future large facilities in the following areas isessential:

Gamma raysNeutrinosDark MatterGravitational Waves

We find that support in the following areas is essential primarilyfor exploitation of current facilities:

CMB-PolCosmic rays

We also encourage innovative ideas and support for smallprojects. Some examples:

Inverse Square Law testeEDM

Future OpportunitiesSome technologies:Gamma rays:Solid state PMT equivalentsDark matter and neutrinos:Liquid noble gasesTPC detectorsSuperconducting cryogenic detectors (e.g. TES, KID)Large format calorimetersGravity waves:Mirror coatingsPrecision range-finding interferometersMechanical isolation suspensionCMB polarisation:Detectors, OMTs, horns/antennas, readouts