GK Seminars WS 14/15

 

Tue 28.10.2014, 16.30 h

V. Schulz (Uniklinik RWTH Aachen)

Basic principles of Positron Emission Tomography (PET) and recent results of an in-house developed PET-system using digital silicon photomultipliers (SiPMs)

 

Tue 04.11.2014, 16.30 h

B. Allanach (Cambridge)

Explaining CMS lepton excesses with supersymmetry

Abstract:
Several CMS analyses involving di-leptons have recently reported small 2.4-2.8 sigma local excesses: nothing to get too excited about, but worth keeping an eye on nonetheless. In particular, a search in the lljj p_T(miss) channel, a search for W_R in the lljj channel and a di-leptoquark search in the lljj channel and ljj p_T(miss) channel have all yielded small excesses. We interpret the first excess in the MSSM, showing that the interpretation is viable in terms of other constraints, despite only having squark masses of around 1 TeV. We can explain the last three excesses with a single R-parity violating coupling that predicts a non-zero contribution to the neutrinoless double beta decay rate.

 

Tue 11.11.2014, 16.30 h

A. Kellerbauer (MPI fuer Kernphysik Heidelberg)

High-Precision Studies with Antihydrogen

Abstract:
After the first production of cold antihydrogen by the ATHENA collaboration at CERN's Antiproton Decelerator, second-generation experiments are being performed and/or being set up with the aim of measuring the fundamental properties of this anti-atom. ALPHA and ATRAP have recently succeeded in storing antihydrogen for extended times and are gearing up for spectroscopic measurements aimed at a test of CPT symmetry. The goal of the AEGIS experiment is to measure the gravitational interaction between matter and antimatter with a pulsed, cold, horizontal antihydrogen beam. Antihydrogen will be produced by charge exchange of cold antiprotons with positronium excited to a Rydberg state. An antihydrogen beam will be formed by a controlled acceleration with an electric-field gradient (Stark acceleration). Subsequently, the free-fall acceleration will be measured with a moiré deflectometer in order to test the weak equivalence principle of General Relativity. In this talk, after an introduction to antimatter physics, the present status of antihydrogen experiments at CERN will be reviewed.

 

Tue 25.11.2014, 16.30 h

T. Marrodan (MPI fuer Kernphysik Heidelberg)

Astrophysical searches for dark matter

Abstract:
Searches for dark matter are motivated by various astronomical and cosmological observations. It is commonly assumed that elementary particles could be the constituents of this new form of non-luminous matter. New particles that could account for dark matter appear in various theories beyond the standard model of particle physics. These new particles could be detected in three different ways: producing them at particle accelerators, looking for products of their self-annihilations at locations where dark matter clusters, or directly detecting them via scattering off a detector's target material. A measurement of WIMPs (Weakly Interacting Massive Particles) scattering off target nuclei would provide valuable information on the dark-matter particle mass and its interaction probability with ordinary matter. After an introduction to the various indications for dark matter and possible candidates, the direct and indirect detection principles will be reviewed in the talk. An overview of current and future direct detection experiments is given, including the most important physics results and prospectives. Special focus will be given to liquid-nobel gas experiments, specifically liquid xenon detectors, which are currently showing the best sensitivity above ~ 6 GeV WIMP mass.  A brief status of the indirect dark matter searches will also be given.

 

Tue 09.12.2014, 16.30 h

T. Golling (Geneva)

Planning for the next discovery with LHC’s Run II

Abstract:
An overview will be given over the extensive ATLAS program of searches for Physics Beyond the Standard Model. The extensions of the Standard Model are attempting to address the open questions we are facing in particle physics - the naturalness of the Higgs mass scale, dark matter, neutrino masses, the origin of flavor-symmetry breaking, unification of gauge forces, the incorporation of gravity into the particle picture - to name but a few. The new physics models considered include Supersymmetry, composite Higgs models, extra dimensions, technicolor, hidden valley and many more. The corresponding new signatures range from spectacular new resonances and excesses in various final states to subtle changes in kinematic distributions. The status, recent results and Run II plans of the ATLAS experiment will be presented.

 

Tue 16.12.2014, 16.30 h

P. Gonzalez (NKI Amsterdam)

Principles of EPID Dosimetry

Abstract:
Radiotherapy uses ionizing radiation to irradiate tumor tissue to a high dose while sparing the surrounding normal healthy tissue as much as possible. To guarantee the safety and quality of a treatment, the dose delivered to a patient has to be verified. Originally designed for patient position verification, Electronic Portal Imagining Devices (EPIDs), provide an elegant solution for dosimetry since they are already available on every treatment machine. At the NKI-AvL we have developed a transmission back-projection model whereby 2D images, acquired with an EPID, are back-projected inside the patient to obtain a 3D dose distribution.

Research in the field of EPID dosimetry focuses on the physics of dose reconstruction. Current research topics include: a) improving the accuracy and verification of our back-projection model for complex radiotherapy treatment types, i.e. gaining a better understanding of the dose delivered by very small and very large radiation fields, b) developing a framework for real-time 3D EPID dose reconstruction, c) Monte-Carlo modeling of the EPID for the new MRI-Linac.

 

Tue 13.01.2015, 16.30 h

A. Schukraft (Fermilab)

The MicroBooNE experiment

 

Tue 20.01.2015, 16.30 h

H. Weber (RWTH)

First measurements of flavour dependence of the Higgs Boson couplings to Leptons with CMS

 

Tue 27.01.2015, 16.30 h

M.G. Pia (INFN Genua)

Geant4: an established instrument and a playground for research

Abstract:
The Geant4 toolkit is widely used to simulate particle interactions with matter in a large variety of research and engineering domains: particle, astroparticle and nuclear physics, astrophysics and space science, medical physics etc. The seminar briefly reviews Geant4 simulation capabilities and applications, and focuses on the validation of Geant4 physics. An overview of recent validation results summarizes the state of the art and highlights open issues in simulation for particle transport. Ongoing efforts to establish methods for the quantification of simulation uncertainties are discussed.

 

Wed 25.02.2015 15:00 - Fri 27.02.2015 11:30

T. Feldmann (Siegen)

Lectures on Factorization in Heavy-Quark Decays

Schedule:

Mi 15.00 - 16:30
Lecture 1:
Effective Hamiltonian for Weak Quark Decays
- Effective Operators
- Wilson Coefficients and Renormalization Group

Do 10.00 - 11.00
Questions for Lecture 1

Do 11.15 - 12.00
Lecture 2A:
Factorization in Heavy-Quark Decays (part A)
- B -> D(*) ell nu and B -> pi(rho) ell nu Transitions in HQET
- B -> D pi Decays and QCDF

Do 14.15 - 15.00
Lecture 2B:
Factorization in Heavy-Quark Decays (part B)
- B -> K pi Decays in QCDF

Do 15.30 - 16.30
Questions for Lecture 2

Fr 10.00 - 11.30
Lecture 3:
Theoretical Issues in B -> K* ell+ ell- Decays
- B -> K* ell+ ell- Decays at Large Recoil (QCDF/SCET)
- B -> K* ell+ ell- at Low Recoil (HQET and Duality)
- "Puzzles" in Recent LHCb measurements