Table of Contents

Draft 3 of Paper

pdf with assignments

Outline for Depth Working Group Report

I. Introduction

II. Existing Measurements of Underground Neutron Backgrounds

Traditionally, underground experiments estimate their neutron backgrounds using extensive simulation normalized to a handful of events in their well-shielded target mass. This leads to large error bars and systematic uncertainties between technologies. A better strategy is to choose a few experiments which are uniquely sensitive to aspects of CMINB and use them to improve the physics and implementation of the simulation package(s) used by all experiments. The current status of these experiments is outlined below.

III. The simulation challenge.

A. Description and Intro

The two simulations in general use by the physics community are Geant4 [12–13] and FLUKA [14–15]. Geant4 is a C++ based toolkit of physics processes, geometry constructors and processing methods used to transport charged particles through matter. It is written, maintained, and validated by the Geant4 collaboration, which consists of high-energy physicists, space scientists, medical physicists and software engineers. The origin of FLUKA (FLUktuierendeKAskade) goes back to 1962 in the context of understanding shielding requirements for a new proton accelerator at CERN. FLUKA is an official project supported by CERN and INFN. It is a fully integrated particle physics Monte Carlo simulation package based on micro-physics models which are benchmarked and tuned against experimental data.

[Geant4] S. Agostinelli, et al. (the Geant4 collaboration), Nuclear Instrumentation Methods A 506 (2003) 250; J. Allison, et al. (the Geant4 collaboration), IEEE Transactions on Nuclear Science 53 (2006) 270.

[FLUKA] A. Ferrari, P.R. Sala, A. Fassò, and J. Ranft, FLUKA: a multi-particle transport code, CERN-2005-10 (2005), INFN/TC_05/11, SLAC-R-773; G. Battistoni, et al. The FLUKA code: Description and benchmarking, American Institute of Physics Conference Proceedings 896 (2007) 31.

B. Muon flux

  1. Description of the Groom Parameterization and the parameter choices made by Mei&Hime (Andrew)
  2. Summary of measurements made in caverns.⇒ (Chao)
  3. Description of the MUSUN program and how it works Prisca combined VK texts and edited
    • above includes uncertainties due to rock density/composition/distribution
  4. Comparisons with Groom parameterization vs MUSUN simulations.
    • MUSUN results from Boulby and Gran Sasso and how they improved things(Vitaly)
    • MUSUN vs Groom at Soudan (and Homestake, if we have info) (Angie)
  5. Comparison of doing muons thru geant vs MUSUN ⇒ (Chao) Edited Summaryupdate Version 3

update Version 4 update Version 6

C. Muon-induced Secondaries underground

  1. Intro: Start with general description of secondary processes and what is involved. [AV: I think we should be very specific about the models here, it's not always clear to people how these processes are executed, and it matters since people might have better ideas or at least be aware of deficiencies in the microscopic physics ]
  2. Compare and contrast how well the Simulations matched data in the experiments called out in II, identifying the differences and problems. For now, just make sure such details are in II, so we can write a summarizing paragraph here later.
  3. Parameterizing Results (Andrew will write a short intro to Mei & Hime methodology)
  4. Status and Outstanding Issues: Explain where sims work well and where they don’t. What fits M&H and what doesn’t.
    • a. Geant4: more neutrons and improved multiplicity (Angie, Soudan Geant4). Muon production of neutrons in scint and lead (Melinda or Anthony) [AV: I think this should be pretty specific about the updates to the models building off of what is in the intro to this section]
    • b. Fluka: What has changed in FLUKA since M&H? Tony
    • c. Comparing Geant4 and FLUKA: In terms of muon-induced neutrons (Anthony, Melinda, Tony). In terms of direct comparison at Homestake (Angie, using Raul's FLUKA files)
    • d. Comparing both to data, referencing experiments from the earlier section (where the experimental limitations are explained and cited in detail)

IV Implications for Dark Matter experiments at Homestake 4850

  1. Intro: Describe the geometries of the Ge and LXe and LAr setups and our methodology
    • Ge: Angie
    • LXe: Monica
    • LAr: Chao
  2. Table of nuclear recoils, giving a definition of the cuts decided upon
  3. Veto strategies and resulting reduction in background
  4. Singles cuts, energy deposition, Detector specific issues (LAr v Ge v LXe)
  5. Predicted event rates and sensitivity reach

V. Scaling to different depths

Soudan study

Scale spectra for deeper site (SNOLab)

Parameterization and Scaling Scheme to deal with Depth

VI. Conclusion

What did we learn about Depth and Uncertainties remaining? List and prioritize needs for the future - what bkgd experiments and sims are needed.