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Princeton Student Finds Bug In LHC Experiment

An anonymous reader writes "A Princeton senior has found a bug in the hardware design for the Compact Muon Solenoid (CMS) experiment of the Large Hadron Collider (LHC). In the hardware used to record and capture events in the LHC, she discovered errors that were leading to the appearances of double images because of particle streams known as jets. 'Xiaohang Quan '09 was working on her senior thesis when she found a miscalculation in the hardware of the world's largest particle accelerator. Quan, a physics concentrator, traveled to Geneva, Switzerland, last week with physics professors Christopher Tully GS '98, Jim Olsen and Daniel Marlow for the annual meeting of the European Organization for Nuclear Research (CERN). This year, however, they also came to discuss Quan's discovery with the designers of the hardware for the Compact Muon Solenoid (CMS) experiment, which, as part of the Large Hadron Collider, has the potential to revolutionize particle physics.'"

7 of 243 comments (clear)

  1. Re:wha? by Quothz · · Score: 5, Informative

    Her last name is "09" and she is a "concentrator?"

    That threw me, too. The '09 appears to be standard form for the Princetonian, representing her (expected) graduation year.

    Who wrote this?

    Tasnim Shamma

    Personal Info

    * Degree: A.B. in English, IPS in Journalism

    * Hometown: Jamaica, NY

    * Contact Email: tasnim.shamma@gmail.com

    Personal Bio

    Princeton '11, Brooklyn Technical High School '07, Daily Princetonian news/blog/multimedia staff, Orange Key tour guide, Daily Princetonian Class of 2001 Summer Journalism Program Alum'06/ Program Staff Associate '08 (www.princeton.edu/sjp), Aspiring Reporter (if there are jobs left when I graduate) ;)

    Off topic: Miss Quan is cute.

  2. Not a hardware bug by rminsk · · Score: 5, Informative

    A Princeton senior has found a bug in the hardware design for the Compact Muon Solenoid (CMS) experiment of the Large Hadron Collider (LHC).

    The bug was in the algorithm analyzing at the data from the CMS and not the hardware.

    1. Re:Not a hardware bug by Anonymous Coward · · Score: 5, Informative

      Actually, not a bug at all. It's a design choice.

      The CMS Global Calorimeter Trigger hardware uses a 3*3 sliding window algorithm to find local maxima (jets) in the calorimeter regions. These 3*3 windows can partially overlap, meaning some energy is double-counted. Having a small amount of double-counted energy has no real consequence on the validity of the triggering, but does greatly simplify the firmware.

  3. Re:Public Spin by JoeBuck · · Score: 4, Informative

    Once again: if there were any chance that LHC could produce earth-swallowing black holes, we'd be dead long ago, because Earth is regularly hit by much more powerful events than anything the LHC will be able to produce.

  4. Re:they should not turn it on by JoeBuck · · Score: 4, Informative

    You are ignorant; the universe is already conducting high-energy physics experiments. They are called cosmic rays, and some of them are billions of times more powerful than the LHC. Yet the earth is still here. And your notion that we delay until we completely understand the laws of physics is comical. What do you think the LHC is for? It's to help us understand the laws of physics! You don't discover laws of physics by just thinking deeply. You discover them by experimentation.

  5. Re:Great story. by Gromius · · Score: 5, Informative

    Its not actually amazingly impressive, its made to sound a lot more impressive than it actually is. One the meeting in question was "CMS week", one of several weeks a year we get all our collaborators together at CERN not CERNs annual meeting. She's basically improved our jet algorithm (as far as I can tell, the article is woefully lacking in details), a decent job for an undergraduate and will certainly help her walk into a PhD place as a shes clearly good enough but she's certainly not the only undergradute to have made a contribution such as this.

  6. Re:they should not turn it on by Gromius · · Score: 4, Informative

    its not really a design flaw. Basically its a minor bug in the algorithms (if I'm reading it right, the article is very confused to say the least) which allow physicists to reconstruct the energies of hadronised partons. Now we can do it a bit better and make slightly better measurements. This software we know isnt optimal, it requires a great deal of knowledge to write and to be honest a major part of the effort in the earily days of an experiment is improving the reconstruction software with fixes such as this. And there will be many more such improvements. Bugs here do not pose any danger because the software is run *after* the event has occured so it cant effect the event, just our understand of what actually happened.

    Also just to make clear that the LHC and CMS are very different things. The LHC is the accelerator and its what makes the particles go very fast. CMS is a detector, it just sits there and records what happens in the collision. CMS is built and designed by a completely different set of people to the LHC. CMS doesnt need the LHC to function and the LHC doesnt need CMS to function but they are a bit pointless without the other.