# Latest **URL:** https://opendata-forum.cern.ch/latest.md [Latest](https://opendata-forum.cern.ch/latest.md) · [Categories](https://opendata-forum.cern.ch/categories.md) --- ## [Welcome to the CERN Open Data forum!](https://opendata-forum.cern.ch/t/welcome-to-the-cern-open-data-forum/7)
**Author:** [@system](https://opendata-forum.cern.ch/u/system)\ **Replies:** 1\ **Last updated:** [11 November 2026 19:49 UTC](https://opendata-forum.cern.ch/t/welcome-to-the-cern-open-data-forum/7 "2026-11-11T19:49:39Z")
Welcome to the CERN Open Data discussion forum! The CERN Open Data portal manages several petabytes of open data from particle physics. The data are released by LHC collaborations in periodic batches after a certain em… --- ## [Experimental OpenSUSE support](https://opendata-forum.cern.ch/t/experimental-opensuse-support/504)
**Author:** [@schwicke](https://opendata-forum.cern.ch/u/schwicke)\ **Replies:** 2\ **Last updated:** [23 October 2026 14:15 UTC](https://opendata-forum.cern.ch/t/experimental-opensuse-support/504 "2026-10-23T14:15:37Z")
A new build for OpenSUSE leap 15 is available on CVMFS, with support for xrootd. The DELPHI stack will require some additional packages, e.g. please run zypper install freetype-devel gcc gcc-c++ gcc-fortran git glibc-de… --- ## [DELPHI software release tag v17102026-1](https://opendata-forum.cern.ch/t/delphi-software-release-tag-v17102026-1/581)
**Author:** [@schwicke](https://opendata-forum.cern.ch/u/schwicke)\ **Replies:** 0\ **Last updated:** [17 October 2026 10:36 UTC](https://opendata-forum.cern.ch/t/delphi-software-release-tag-v17102026-1/581 "2026-10-17T10:36:04Z")
A new maintenance release of the DELPHI software stack is being deployed. v17102026-1 Maintenance release. Changes: phdst: protection against array overflow, affecting LEP1 long DST creation anacra43 fix a regression… --- ## [Simple guide to find basic data and get into XL](https://opendata-forum.cern.ch/t/simple-guide-to-find-basic-data-and-get-into-xl/394)
**Author:** [@chris\_pav](https://opendata-forum.cern.ch/u/chris_pav)\ **Replies:** 22\ **Last updated:** [13 October 2026 09:09 UTC](https://opendata-forum.cern.ch/t/simple-guide-to-find-basic-data-and-get-into-xl/394 "2026-10-13T09:09:40Z")
Apologies for this question, but having been searching the CERN site for a day or so and not able to find a beginners guide on steps I need to take. My data needs are very basic… and was hoping for some help here to do … --- ## [DELPHI software release tag v10102026-1](https://opendata-forum.cern.ch/t/delphi-software-release-tag-v10102026-1/580)
**Author:** [@schwicke](https://opendata-forum.cern.ch/u/schwicke)\ **Replies:** 0\ **Last updated:** [10 October 2026 05:57 UTC](https://opendata-forum.cern.ch/t/delphi-software-release-tag-v10102026-1/580 "2026-10-10T05:57:18Z")
A new maintenance release of the DELPHI software stack is available. v10102026-1 Maintenance release simana (LEP1 versions) longdst.cra and shortdst.cra: implement protection against an array overflow in pathological … --- ## [Difficulty in Finding gg-\>ZZ\* continuum in Monte-Carlo](https://opendata-forum.cern.ch/t/difficulty-in-finding-gg-zz-continuum-in-monte-carlo/579)
**Author:** [@guest\_hkeoshkerian](https://opendata-forum.cern.ch/u/guest_hkeoshkerian)\ **Replies:** 2\ **Last updated:** [6 October 2026 05:26 UTC](https://opendata-forum.cern.ch/t/difficulty-in-finding-gg-zz-continuum-in-monte-carlo/579 "2026-10-06T05:26:33Z")
Hello, I’ve been trying to locate the gg2ZZ samples in Monte-Carlo in the 2025 ATLAS Metadata. Where can I find these samples? I have been running an H-\>ZZ-\>4l analysis, and have an overall discrepancy of ~1.4 outside t… --- ## [DELPHI software release tag v30092026-1](https://opendata-forum.cern.ch/t/delphi-software-release-tag-v30092026-1/576)
**Author:** [@schwicke](https://opendata-forum.cern.ch/u/schwicke)\ **Replies:** 0\ **Last updated:** [1 October 2026 06:29 UTC](https://opendata-forum.cern.ch/t/delphi-software-release-tag-v30092026-1/576 "2026-10-01T06:29:23Z")
A new maintenance release of the DELPHI software stack is available. v30092026-1 Maintenance release Rebase on OpenPHIGS 0.64, implementing bug fixes and improving support for transparency Bug fixes in the event displ… --- ## [ATLAS Top Tagging Open Data Set](https://opendata-forum.cern.ch/t/atlas-top-tagging-open-data-set/573)
**Author:** [@abdullam](https://opendata-forum.cern.ch/u/abdullam)\ **Replies:** 2\ **Last updated:** [18 September 2026 11:38 UTC](https://opendata-forum.cern.ch/t/atlas-top-tagging-open-data-set/573 "2026-09-18T11:38:27Z")
Hi what is the best way, if any, to stream ATLAS Top Tagging Open Data Set | CERN Open Data Portal | CERN Open Data Portal into a colab notebook, with some persistent storage ? The idea is to run the dataset training us… --- ## [Particle-level truth information?](https://opendata-forum.cern.ch/t/particle-level-truth-information/570)
**Author:** [@jackersc](https://opendata-forum.cern.ch/u/jackersc)\ **Replies:** 1\ **Last updated:** [14 August 2026 22:44 UTC](https://opendata-forum.cern.ch/t/particle-level-truth-information/570 "2026-08-14T22:44:04Z")
Hello, I am looking for a specific kind of HEP dataset and I was wondering wether it’s possible to extract something like that from the ATLAS open data. I basically want a different version of the Omnifold dataset (Lar… --- ## [DELPHI release tag v24072026-1](https://opendata-forum.cern.ch/t/delphi-release-tag-v24072026-1/567)
**Author:** [@schwicke](https://opendata-forum.cern.ch/u/schwicke)\ **Replies:** 0\ **Last updated:** [25 July 2026 06:53 UTC](https://opendata-forum.cern.ch/t/delphi-release-tag-v24072026-1/567 "2026-07-25T06:53:33Z")
A new maintenance release of the DELPHI software stack is becoming available. This release only affects the event display functionality. v24072026-1 Maintenance release Rebase on OpenPHIGS 0.62, fixing clipping and po… --- ## [DELPHI software release tag v28062026-1](https://opendata-forum.cern.ch/t/delphi-software-release-tag-v28062026-1/566)
**Author:** [@schwicke](https://opendata-forum.cern.ch/u/schwicke)\ **Replies:** 1\ **Last updated:** [1 July 2026 14:19 UTC](https://opendata-forum.cern.ch/t/delphi-software-release-tag-v28062026-1/566 "2026-07-01T14:19:18Z")
Dear all, A new DELPHI software release is becoming available on CVMFS, v28062026-1. Most significant changes are: Update of PDL file lists, curation of data. Multiple updates and bug fixes in the event display: this … --- ## [Mutiple FILE in PDLINPUT](https://opendata-forum.cern.ch/t/mutiple-file-in-pdlinput/565)
**Author:** [@xyv-6vqgpb](https://opendata-forum.cern.ch/u/xyv-6vqgpb)\ **Replies:** 2\ **Last updated:** [28 June 2026 08:17 UTC](https://opendata-forum.cern.ch/t/mutiple-file-in-pdlinput/565 "2026-06-28T08:17:30Z")
Hello! I’m using examples/dump in the Docker container, and I have this PDLINPUT: FILE = /mnt/e/DELPHI/Data/1994/Y13709.100.al FILE = /mnt/e/DELPHI/Data/1994/Y13709.101.al but dump only reads one file. How can I inst… --- ## [Missing MC background in 93928](https://opendata-forum.cern.ch/t/missing-mc-background-in-93928/562)
**Author:** [@11482772258765412902](https://opendata-forum.cern.ch/u/11482772258765412902)\ **Replies:** 1\ **Last updated:** [18 June 2026 03:55 UTC](https://opendata-forum.cern.ch/t/missing-mc-background-in-93928/562 "2026-06-18T03:55:59Z")
Hi, I’m trying to do the 4leptons analysis with ATLAS data15+16, but parts of MC backgrounds process are missing, for example: ODEO\_FEB2025\_v0\_exactly4lep\_mc\_302523.Pythia8EvtGen\_A14NNPDF23LO\_2DP20\_Mass\_250\_400.exactly4… --- ## [Problem with key(?)](https://opendata-forum.cern.ch/t/problem-with-key/559)
**Author:** [@harr](https://opendata-forum.cern.ch/u/harr)\ **Replies:** 1\ **Last updated:** [8 June 2026 08:56 UTC](https://opendata-forum.cern.ch/t/problem-with-key/559 "2026-06-08T08:56:12Z")
My students are having a problem when trying to access the DoubleParked\_Muons data, stopping while trying to access a private key. Do you have any suggestions? Thanks\> When attempting to run the dimuon spectrum analy… --- ## [SM background MC available for the 2024r-pp Run 3 ](https://opendata-forum.cern.ch/t/sm-background-mc-available-for-the-2024r-pp-run-3/556)
**Author:** [@maboryso](https://opendata-forum.cern.ch/u/maboryso)\ **Replies:** 7\ **Last updated:** [26 May 2026 20:51 UTC](https://opendata-forum.cern.ch/t/sm-background-mc-available-for-the-2024r-pp-run-3/556 "2026-05-26T20:51:39Z")
Hi, I am working with the ATLAS Open Data 2024r-pp release for a research project using the atlasopenmagic I have a few questions: Could you confirm that the MC samples available in the 2024r-pp release via atlasopen… --- ## [EventInfoAuxDyn\_mcEventWeights](https://opendata-forum.cern.ch/t/eventinfoauxdyn-mceventweights/546)
**Author:** [@fjumawan](https://opendata-forum.cern.ch/u/fjumawan)\ **Replies:** 11\ **Last updated:** [14 April 2026 15:29 UTC](https://opendata-forum.cern.ch/t/eventinfoauxdyn-mceventweights/546 "2026-04-14T15:29:49Z")
Hi everyone, I am currently working with ATLAS Open Data to test a Machine Learning algorithm for background estimation. I am manually streaming/downloading ROOT files rather than using the standard atlas-open-magic pac… --- ## [Open EvtGen: ttbar semileptonic with muon filter?](https://opendata-forum.cern.ch/t/open-evtgen-ttbar-semileptonic-with-muon-filter/538)
**Author:** [@rakhi](https://opendata-forum.cern.ch/u/rakhi)\ **Replies:** 9\ **Last updated:** [18 March 2026 20:17 UTC](https://opendata-forum.cern.ch/t/open-evtgen-ttbar-semileptonic-with-muon-filter/538 "2026-03-18T20:17:38Z")
Dear EvtGen team, Do you happen to have samples with ttbar → mu + nu + jets at 13.6 TeV? I’m questioning the wisdom of downloading dataset 601229 (PhPy8EG\_A14\_ttbar\_hdamp258p75\_SingleLep) for which I would need to requ… --- ## [JupyterLab C++ ROOT](https://opendata-forum.cern.ch/t/jupyterlab-c-root/539)
**Author:** [@guest\_bernard.chaura](https://opendata-forum.cern.ch/u/guest_bernard.chaura)\ **Replies:** 30\ **Last updated:** [14 March 2026 15:47 UTC](https://opendata-forum.cern.ch/t/jupyterlab-c-root/539 "2026-03-14T15:47:57Z")
JupyterLab C++ ROOT does not suport multicore. Passing 10fb to 39fb very long to run with labtop More events less speed to run --- ## [Question about Sh\_2214\_Wmunu\_maxHTpTV2\_CFilterBVeto](https://opendata-forum.cern.ch/t/question-about-sh-2214-wmunu-maxhtptv2-cfilterbveto/524)
**Author:** [@rakhi](https://opendata-forum.cern.ch/u/rakhi)\ **Replies:** 8\ **Last updated:** [13 March 2026 16:40 UTC](https://opendata-forum.cern.ch/t/question-about-sh-2214-wmunu-maxhtptv2-cfilterbveto/524 "2026-03-13T16:40:12Z")
The metadata for evtgen dataset 700781 reads as follows: {‘dataset\_number’: ‘700781’, ‘physics\_short’: ‘Sh\_2214\_Wmunu\_maxHTpTV2\_CFilterBVeto’, ‘e\_tag’: None, ‘cross\_section\_pb’: 22935.0, ‘genFiltEff’: 0.1484349, ‘k… --- ## [Thank You from a Graduate Student Using ATLAS Open Data](https://opendata-forum.cern.ch/t/thank-you-from-a-graduate-student-using-atlas-open-data/537)
**Author:** [@bernadulger](https://opendata-forum.cern.ch/u/bernadulger)\ **Replies:** 1\ **Last updated:** [11 February 2026 21:55 UTC](https://opendata-forum.cern.ch/t/thank-you-from-a-graduate-student-using-atlas-open-data/537 "2026-02-11T21:55:25Z")
Hello, First of all, I wasn’t entirely sure which category to select, so I chose “uncategorized.” If that was incorrect, I sincerely apologize. My name is Berna Dülger, and I’m a final-year student at Erciyes Universit… --- ## [Request for access to LHCb Lambda\_b^0 → p K pi pi decay data (Nature 2025 CP violation paper)](https://opendata-forum.cern.ch/t/request-for-access-to-lhcb-lambda-b-0-p-k-pi-pi-decay-data-nature-2025-cp-violation-paper/535)
**Author:** [@10999983717345018037](https://opendata-forum.cern.ch/u/10999983717345018037)\ **Replies:** 0\ **Last updated:** [11 February 2026 21:54 UTC](https://opendata-forum.cern.ch/t/request-for-access-to-lhcb-lambda-b-0-p-k-pi-pi-decay-data-nature-2025-cp-violation-paper/535 "2026-02-11T21:54:06Z")
Dear LHCb Open Data Team, I am an independent researcher testing a theoretical prediction correlating CP violation phases with baryon internal structure factors. I previously contacted opendata-support@cern.ch (20 Janua… --- ## [DELPHI software release v04022026](https://opendata-forum.cern.ch/t/delphi-software-release-v04022026/531)
**Author:** [@schwicke](https://opendata-forum.cern.ch/u/schwicke)\ **Replies:** 0\ **Last updated:** [4 February 2026 17:38 UTC](https://opendata-forum.cern.ch/t/delphi-software-release-v04022026/531 "2026-02-04T17:38:41Z")
There is a new release of the DELPHI software available, v04022026. Changes mostly include bug fixes, and rebuilds of container images, fixing initialization issues for xrootd enabled containers. Feedback is appreciate… --- ## [Open Evtgen: incompatibility between hepmc version number (2) given in metadata and the version number written in the hepmc file](https://opendata-forum.cern.ch/t/open-evtgen-incompatibility-between-hepmc-version-number-2-given-in-metadata-and-the-version-number-written-in-the-hepmc-file/530)
**Author:** [@rakhi](https://opendata-forum.cern.ch/u/rakhi)\ **Replies:** 3\ **Last updated:** [1 February 2026 10:15 UTC](https://opendata-forum.cern.ch/t/open-evtgen-incompatibility-between-hepmc-version-number-2-given-in-metadata-and-the-version-number-written-in-the-hepmc-file/530 "2026-02-01T10:15:06Z")
Dear open data team, In some evtgen samples (e.g. dataset 410472) the metadata states that the files are in hepmc2 format, whilst if you read the top of (at least some of) the hepmc files, they actually say “HepMC::Vers… --- ## [Downloading the DEPLHI data](https://opendata-forum.cern.ch/t/downloading-the-deplhi-data/522)
**Author:** [@lukesm](https://opendata-forum.cern.ch/u/lukesm)\ **Replies:** 1\ **Last updated:** [17 December 2025 17:18 UTC](https://opendata-forum.cern.ch/t/downloading-the-deplhi-data/522 "2025-12-17T17:18:31Z")
My goal is to create a copy of all the DELPHI data for Open Science II. I am using the cernopendata-client to handle the downloads, and I encountered two errors that I believe are not on my side. First error: $ cernope… --- ## [Download all files in one evtgen dataset using https protocol](https://opendata-forum.cern.ch/t/download-all-files-in-one-evtgen-dataset-using-https-protocol/518)
**Author:** [@rakhi](https://opendata-forum.cern.ch/u/rakhi)\ **Replies:** 4\ **Last updated:** [8 December 2025 13:43 UTC](https://opendata-forum.cern.ch/t/download-all-files-in-one-evtgen-dataset-using-https-protocol/518 "2025-12-08T13:43:14Z")
Is there a quick way to download all hepmc files in one evtget dataset from outside CERN, similar to e.g. Downloading all the files for a dataset together but for evtgen? --- ## [Atlas Open Data and GRLs](https://opendata-forum.cern.ch/t/atlas-open-data-and-grls/519)
**Author:** [@10284879194598608039](https://opendata-forum.cern.ch/u/10284879194598608039)\ **Replies:** 1\ **Last updated:** [29 November 2025 22:33 UTC](https://opendata-forum.cern.ch/t/atlas-open-data-and-grls/519 "2025-11-29T22:33:42Z")
Hello, I have read the documentation and came across the definition of GRLs and LBs. Now I didn’t quite understand whether I need to apply this selection myself or is the data released is already filtered. --- ## [No data available for dataset 601226](https://opendata-forum.cern.ch/t/no-data-available-for-dataset-601226/517)
**Author:** [@rakhi](https://opendata-forum.cern.ch/u/rakhi)\ **Replies:** 5\ **Last updated:** [20 November 2025 12:28 UTC](https://opendata-forum.cern.ch/t/no-data-available-for-dataset-601226/517 "2025-11-20T12:28:36Z")
\--------------------------------------------------------------------------- ValueError Traceback (most recent call last) /tmp/ipython-input-2541026952.py in \() ----\> 1 atom.ge… --- ## [Help for EVTGEN dataset naming convention and physics\_short explanation](https://opendata-forum.cern.ch/t/help-for-evtgen-dataset-naming-convention-and-physics-short-explanation/515)
**Author:** [@rakhi](https://opendata-forum.cern.ch/u/rakhi)\ **Replies:** 4\ **Last updated:** [19 November 2025 14:36 UTC](https://opendata-forum.cern.ch/t/help-for-evtgen-dataset-naming-convention-and-physics-short-explanation/515 "2025-11-19T14:36:34Z")
Please could someone point me to where I can find explanations for the file naming conventions for the EVTGEN datasets (physics\_short info)? I can no longer find it. --- ## [Newbie question on atlasopenmagic keyword multiple query terms](https://opendata-forum.cern.ch/t/newbie-question-on-atlasopenmagic-keyword-multiple-query-terms/514)
**Author:** [@rakhi](https://opendata-forum.cern.ch/u/rakhi)\ **Replies:** 5\ **Last updated:** [19 November 2025 13:12 UTC](https://opendata-forum.cern.ch/t/newbie-question-on-atlasopenmagic-keyword-multiple-query-terms/514 "2025-11-19T13:12:11Z")
How do I query multiple keywords linked with an AND in an EVTGEN dataset? I tried e.g. atom.match\_metadata(field=‘keywords’, value=r"(?=.\*top)(?=.\*Alternative)") atom.match\_metadata(field=‘keywords’, value=(‘top’, ‘Alt… --- ## [Observation of a Double Peak in the Dijet Invariant Mass Spectrum Using NanoAOD Data](https://opendata-forum.cern.ch/t/observation-of-a-double-peak-in-the-dijet-invariant-mass-spectrum-using-nanoaod-data/487)
**Author:** [@karen.bustamante](https://opendata-forum.cern.ch/u/karen.bustamante)\ **Replies:** 1\ **Last updated:** [1 November 2025 13:57 UTC](https://opendata-forum.cern.ch/t/observation-of-a-double-peak-in-the-dijet-invariant-mass-spectrum-using-nanoaod-data/487 "2025-11-01T13:57:40Z")
I calculated the invariant mass of dijets using the JetHT primary dataset in NanoAOD format from Run H of 2016 (/JetHT/Run2016H-UL2016\_MiniAODv2\_NanoAODv9-v1/NANOAOD). For this test, I worked with a single file: root://… [Next page](https://opendata-forum.cern.ch/latest.md?page=1)