Dr Ulla Blumenschein

Dr Ulla Blumenschein

Lecturer in Particle Physics
Address:
School of Physics and Astronomy
Queen Mary, University of London
327 Mile End Road, London, E1 4NS

Telephone: 020 7882 6967
Room: G O Jones 407
Email:

 

I am interested in the fundamental forces in nature, which in our current model are introduced by imposing local symmetries on the Lagrangian density. By recreating conditions of the early universe in powerful synchrotrons like the Large Hadron Collider (LHC), we aim to improve our understanding of the  various forces with the hope to eventually be able to describe them in a unified theory.

Due to novel theoretical approaches, the precision of the theoretical predictions for interaction rates in high-energy collisions has increased dramatically over the past years, promptingus to test the prediction at a high precision level, with the option to find signs for new physics in deviations from the current models. In the ATLAS experiment, I have been investigating in particular the Strong Force by measuring processes where jets of hadrons are produced in association with the massive carriers of the weak force (JHEP 07 (2013) 032 Eur. Phys. J. C77 (2017) 361). Since they result in  similar final states as the production of new particles they have to be described at a high precision, lest we confuse them with the latter. Currently I am focusing on a special class of these processes where the hadronic jets are initiated by heavy bottom or charm quarks. The description of such processes provides additional challenges for theory and several  so far barely tested approaches are advertised to predict them with high precision.

In our Standard Model, the breaking of Electroweak symmetry by the Higgs field leads to massive force carriers and Higgs bosons. The later has been  discovered by ATLAS and CMS experiments in 2012 in interactions with electroweak gauge bosons. In contrast, we have only recently  obtained first evidence for the  Yukawa coupling of the Higgs field to fermions, which is expected to generate the fermion masses. I have participated in this measurement in ATLAS which selected  Higgs decays into two  tau leptons  (JHEP 04 (2015) 117) and I am involved in a follow-up  measurement  at nearly twice the center-of-mass energy. I am now starting to work on a measurement of Higgs decays into massive bottom quarks. First evidence for this process has just been reported and with a larger data set we expect to be a able to not only observe the process with higher significance but as well to measure key kinematic distributions of the decay products. I want to focus in particular on the associated production of a Higgs boson and an electroweak gauge boson for which the  above mentioned associated direct production of electroweak bosons with bottom quarks constitutes  a major background.

 

In 2017/18, I am teaching the following courses:

 - SPA4601 Professional Skills for Scientists (1st year, Semester A, deputy modul organizer)
 - SPA4321 Introduction to C++ (1st year, Semester B, modul organizer)
 - SPA7029U/P Collider Physics (4th year, Semester B, deputy module organizer)

I am also organising the NExT School 25-28 June 2018

PhD students:
  Jacob Oliver: Production of Z bosons in association with bottom and charm quarks at ATLAS

 

Conference organisation

- SMatLHC 2014 EWK sessions
- ICHEP 2014 QCD sessions
- LHCP 2017 EWK sessions
- EPS 2017 QCD sessions
 
Talks at international conferences:

- Sfermions at LEP2, Higgs and Supersymmetry Conference, 2001 in Orsay on behalf of the LEP experiments.
- Limits on the mass of the lightest supersymmetric particle at LEP, 16th Int. Conf. on Particles and Nuclei (PANIC) 2002 in Osaka on behalf of the LEP experiments.
- Search for Associate Chargino Neutralino Production in Trilepton Final States , Meeting of the Division of Particles and Fields of the American Physical Society, (DPF) 2004 in Riverside, on behalf of the D0 Collaboration.
- Jets and Jets+MET Studies at the LHC , Rencontres de Moriond, QCD and High Energy Interactions 2008, on behalf of the ATLAS Collaboration.
- ATLAS WZ Physics, LHC days 2010 in Split, Croacia, on behalf of the ATLAS Collaboration.
- ATLAS W/Z+jets, LHC EW WG meeting, Nov 2011 in Geneva, on behalf of the ATLAS Collaboration.
- ATLAS SM and top Physics, 13th Marcel Grossmann Meeting, July 2012 in Stockholm, on behalf of the ATLAS Collaboration.
- Measurements of the production of vector bosons in association with heavy flavour quarks at the LHC, LHCP in New York, June 2014,on behalf of the ATLAS Collaboration.
- Top and electroweak measurements , plenary presentation at the 38th International Conference on High Energy Physics (ICHEP 2016) in Chicago, August 2016.

 

Publications with significant contributions
- A. Heister et al., [ALEPH Collaboration],Absolute Lower Limits on the Masses of Selectrons and Sneutrinos in the MSSM , Phys. Lett. B 544 (2002) 73-88.
- V.~M.~Abazov et al. [D0 Collaboration], Search for supersymmetry via associated production of charginos and neutralinos in final states with three leptons , Phys. Rev. Lett. 95 (2005) 151805.
- K. J. Anderson et al., A Mobile Data Acquisition System , JINST 2, P07002 (2007).
- G.~Aad et al. [ATLAS Collaboration], Measurement of the Z to tau tau cross section with the ATLAS detector , Phys. Rev. D 84, 112006 (2011).
- G.~Aad et al. [ATLAS Collaboration], Measurement of the production cross section for W-bosons in association with jets in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector , Phys. Lett. B 698 (2011) 325.
- G.~Aad et al. [ATLAS Collaboration], Measurement of the production cross section for Z/gamma* in association with jets in $pp$ collisions at $\sqrt{s}=7$ TeV with the ATLAS detector , Phys. Rev. D 85 (2012) 032009.
- G.~Aad et al. [ATLAS Collaboration], Search for the Standard Model Higgs boson in the H to tau+ tau- decay mode in sqrt{s}=7 TeV pp collisions with ATLAS , JHEP {09} (2012) 070.
- G.~Aad et al. [ATLAS Collaboration], Measurement of the production cross section of jets in association with a Z boson in pp collisions at sqrt{s} = 7 TeV with the ATLAS detector , JHEP 07(2013) 032.
- G.~Aad et al.[ATLAS Collaboration], Evidence for the Higgs-boson Yukawa coupling to tau leptons with the ATLAS detector , JHEP 04 (2015) 117.
- G.~Aad et al. [ATLAS Collaboration], Identification and energy calibration of hadronically decaying tau leptons with the ATLAS experiment in pp colllisions at sqrt{s} = 8$ TeV , Eur. Phys. J. C (2015).
- U.~Blumenschein, Jet production in association with vector bosons or top quarks ,Int. J. Mod. Phys. A, 30, 1546007 (2015).
- G.~Aad at al. [ATLAS Collaboration], Measurement of W and Z-boson production cross sections in pp collisions at sqrt{s} = 13$ TeV with the ATLAS detector , arXiv:1603.09222, Phys. Lett. B 759 (2016) 601

- G.~Aad at al. [ATLAS Collaboration], Measurements of the production cross section of a Z boson in association with jets in pp collisions at sqrt(s) =13 TeV with the ATLAS detector , Eur. Phys. J. C77 (2017) 361.

All publications

Master Classes:
In 2018, I am going to organise the EPPOG Master Classes in QMUL