{
  "id": 57568,
  "title": "Particles that don't hit",
  "url": "/competitions/trackml-particle-identification/discussion/57568",
  "author_name": "",
  "post_date": "2018-05-25T12:15:45.433088Z",
  "votes": null,
  "comment_count": 3,
  "views": 0,
  "content": "<p>I have a question on how can the particles with nhits=0 be detected if no detector accounts for them?</p>",
  "messages": [
    {
      "id": "333564",
      "postDate": "05/25/2018 12:15:45",
      "content": "<p>I have a question on how can the particles with nhits=0 be detected if no detector accounts for them?</p>",
      "rawMarkdown": "I have a question on how can the particles with nhits=0 be detected if no detector accounts for them?",
      "votes": null
    },
    {
      "id": "333674",
      "postDate": "05/25/2018 16:43:38",
      "content": "<p>They are noise detections.\nThat's why it's not one hit.\nAccording to <a href=\"https://github.com/LAL/trackml-library\">documentation</a> ('A value of 0 means that the hit did not originate from a reconstructible particle, but e.g. from detector noise')</p>",
      "rawMarkdown": "They are noise detections.\nThat's why it's not one hit.\nAccording to [documentation][1] ('A value of 0 means that the hit did not originate from a reconstructible particle, but e.g. from detector noise')\n\n\n  [1]: https://github.com/LAL/trackml-library",
      "votes": null
    },
    {
      "id": "333982",
      "postDate": "05/26/2018 07:56:32",
      "content": "<p>The particles file is the ground truth of all particles in the event. Some of them (mostly secondary particles created by the interaction of primary particles in the detector, this can be seen by sqrt(vx*<em>2+vy</em>*2) &gt;&gt; 10 mm, and in fact much large, close to the exit of the detector ) do not cross any detector module by chance, so they have zero hits.   </p>",
      "rawMarkdown": "The particles file is the ground truth of all particles in the event. Some of them (mostly secondary particles created by the interaction of primary particles in the detector, this can be seen by sqrt(vx**2+vy**2) &gt;&gt; 10 mm, and in fact much large, close to the exit of the detector ) do not cross any detector module by chance, so they have zero hits.",
      "votes": null
    },
    {
      "id": "333983",
      "postDate": "05/26/2018 07:58:25",
      "content": "<p>hits with particle_id zero are indeed noise hits, not caused by any particles. This is different from particles causing zero hits.</p>",
      "rawMarkdown": "hits with particle_id zero are indeed noise hits, not caused by any particles. This is different from particles causing zero hits.",
      "votes": null
    }
  ],
  "comments": [
    {
      "id": 333674,
      "author_name": "darkdoval",
      "author_url": "",
      "post_date": "05/25/2018 16:43:38",
      "content": "<p>They are noise detections.\nThat's why it's not one hit.\nAccording to <a href=\"https://github.com/LAL/trackml-library\">documentation</a> ('A value of 0 means that the hit did not originate from a reconstructible particle, but e.g. from detector noise')</p>",
      "votes": null,
      "replies": [
        {
          "id": 333983,
          "author_name": "droussea",
          "author_url": "",
          "post_date": "05/26/2018 07:58:25",
          "content": "<p>hits with particle_id zero are indeed noise hits, not caused by any particles. This is different from particles causing zero hits.</p>",
          "votes": null,
          "replies": []
        }
      ]
    },
    {
      "id": 333982,
      "author_name": "droussea",
      "author_url": "",
      "post_date": "05/26/2018 07:56:32",
      "content": "<p>The particles file is the ground truth of all particles in the event. Some of them (mostly secondary particles created by the interaction of primary particles in the detector, this can be seen by sqrt(vx*<em>2+vy</em>*2) &gt;&gt; 10 mm, and in fact much large, close to the exit of the detector ) do not cross any detector module by chance, so they have zero hits.   </p>",
      "votes": null,
      "replies": []
    }
  ],
  "raw_markdown_by_id": {
    "333564": "I have a question on how can the particles with nhits=0 be detected if no detector accounts for them?",
    "333674": "They are noise detections.\nThat's why it's not one hit.\nAccording to [documentation][1] ('A value of 0 means that the hit did not originate from a reconstructible particle, but e.g. from detector noise')\n\n\n  [1]: https://github.com/LAL/trackml-library",
    "333982": "The particles file is the ground truth of all particles in the event. Some of them (mostly secondary particles created by the interaction of primary particles in the detector, this can be seen by sqrt(vx**2+vy**2) &gt;&gt; 10 mm, and in fact much large, close to the exit of the detector ) do not cross any detector module by chance, so they have zero hits.",
    "333983": "hits with particle_id zero are indeed noise hits, not caused by any particles. This is different from particles causing zero hits."
  },
  "source": "meta"
}