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Documented variables used for likelihood selection (10.03.2015)


In cosmic-rays production models Deuterons and Anti-Deuterons are created from spallation reaction between Cosmic Ray (CR) primaries (mostly p, anti-p and He) with nuclei of ISM (p and He). In the Antideuterons case, this secondary contribute could be accompanied by an important input due to Dark Matter (DM) annihilation. The magnitude of this primary contribution is largely dependent on the DM mass and cross sections, The main advantage of Anti-Deuterons, compared to the predictions for the anti-p - is that the primary Anti-Deuteron flux should be up to three orders of magnitude higher with respect to the secondary one in a wide range of possible annihilating Dark Matter masses. Anti-Deuterons remains an ultra-rare signal, even assuming DM annihilation contribution. So the discovery of a substantial amount of Anti-Deuterons in Cosmic-Rays could be an important indirect evidence for Dark Matter annihilation in space. Although not designed for that particular purpose, AMS-02 experiment on the International Space Station have some potential for discovery (or setting an upper bound) on the Anti-Deuteron flux, due to his high acceptance, isotopic distinction power and very long expected observation time (from 10 to 20 years).

Measurement of a Deuteron flux is a first step in preparation for the study of the cosmic Anti-Deuteron flux, allowing us to understand better the performance of the detector and to optimize the selection strategy. Moreover the deuteron flux measure is itself very important, because the flux ratio between exclusively secondary and primary produced CR particle gives important constraint to the propagation models of CR in the Galaxy. We developed a multivariate approach for the distinction of deuterons from the overwhelming protons background, based on the concept of non-euclidian distance in 3-dimensional space of the variables used for p/d distinction (momentum, Beta, Energy deposition), obtaining a very high purity of the deuterons signal. As soon as consolidated, this approach will be applied for the more challenging antideuterons search in CR.

Analysis strategy


The preselection requires events with exactly one track, exactly one downgoing particle with charge=1. Also we require a number of minimum bias and golden selection cuts:

* TRD * Tracker * TOF * RICH

Cleaning multiple interactions

Likelihood discriminant is used to clean a sample (MC or Data) form the events with multiple interactions. The following variables are entering the discriminant.

Varable Description Code sample
NAnticluster Number of ACC clusters NAnticluster = event->NAntiCluster();
unusedTOF Number of unused TOF clusters unusedTOF = event->NTofCluster() - event->pBeta(0)->NTofCluster();
Chi2 Chi-square of the track fit Chi2 = track->GetChisq( track->iTrTrackPar(1,3,1));
unusedLayers Number of unused inner tracker layers
 int unusedLayers = 0;
 int fitID3 = track->iTrTrackPar(1,3,1); 
 TrTrackPar parameters = track->gTrTrackPar(fitID3);
  for (int layer=2;layer<9;layer++) 
     if(!parameters.TestHitLayerJ(layer)) unusedLayers++;
diffR Difference between upper and lower rigidity
Rup = track->GetRigidity( track->iTrTrackPar(1,1,1));
Rdown = track->GetRigidity(track->iTrTrackPar(1,2,1));
R = track->GetRigidity(track->iTrTrackPar(1,3,1));

diffR = fabs(Rup-Rdown)/R
fuoriX Erm.... oh boy

Multivariate deuteron selection

Flux extraction

Exposure time


Template fit

Working on analysis code

First you need to checkout the git repository

git clone -b francesco

That will create an AMSDeutons directory with all the source codes in it. If you already have that directory and you need to update its contents from github server, then you should cd onto it and issue

git pull

If your work is up-to-date you can work on the code. You can check the changes you've made by issuing

git status

It will tell you which files was created, deleted or modified.

To upload the results on the github server you need to execute

git push

Monte Carlo files






-- KostyaKanishchev - 2015-03-04

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Topic revision: r6 - 2015-04-21 - KostyaKanishchev
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