Please return to : Olaf Behnke ZEUS/F1  01a/O1.132    Tel. 3854
   or email  to   : obehnke@mail.desy.de,doris.eckstein@desy.de


   Request for a DESY Summer Student in 2013
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   Name : Carmen Diez Pardos   email : carmen.diez@desy.de     
  
   Tel  :  1797                Room : 1B 02.204
 
   DESY-Group/Experiment : CMS

 
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   Short description of the project the student should work on  :

   The CMS top group is performing measurement of additional particle jets in events with top-anti-top quark pairs at the LHC. The fraction of tt events with additional hard jets in the final state is about half of the total number of events. The understanding of these processes is crucial to constrain ISR/FSR and provides a test of QCD at the LHC energy regime. Also new physics can potentially manifest in top final states, so tt+jets is a background for many searches. 

   The jet activity in top-antitop quark pair events was studied using the dataset recorded in 2011 (5/fb integrated luminosity) in the dileptonic decay channels. We    measured the differential top anti-top quark cross section as a function of the jet multiplicity. Furthermore, the distribution of the fraction of events without additional jets above a momentum threshold is measured. Several QCD calculations are compared with the data. The summer student would contribute to this effort, taking part in the analysis of the data sample collected at a center of mass energy of 8 TeV during 2012. The large statistics of the full 2012 dataset will allow to study  quantitatively the agreement between the measurement with different theory predictions. 


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   Physics / Computing/ Engineering  Content of the project :

   Physics: Data Analysis, Top Quark phyics

   Computing: Learning the ROOT architecture of HEP analysis and 
   the CMSSW software environment used by CMS
 

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  Special Qualifications expected from the student ( Computing,...) :
 
  Basic programming experience.
  Some knowledge of linux, C++, ROOT, python is helpful but not required.

 
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  Other remarks :  

  None 

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   Supervisor(s) during the project (16/07/13 - 5/09/13) :
 
  
   Name: Carmen Diez Pardos     Tel: 1797       email: carmen.diez@desy.de