Hon.-Prof. Allen C. Caldwell

Lehrveranstaltungen und Termine

Ausgeschriebene Angebote für Abschlussarbeiten

Analysis of the Pixel Vertex Detector performance during BEAST Phase 2

For the commissioning phase of the upgraded accelerator SuperKEKB a special detector

system (BEAST) substitutes the inner tracking system. It consists of several subdetectors

and its purpose is to give feedback for the accelerator operation and monitor the

background levels. One part of this BEAST detector is a subset of four PXD modules

which are arranged in two layers. Beginning of 2018 all Belle II subdetectors including

the PXD modules run successfully during the cosmic run and detected the first particle

tracks. The accelerator will start operation soon and first collisions are expected in May,

completing this initial data taking by mid July (“Phase 2”). The task is to analyze the

data from this phase to extract information on the PXD performance and its vertex

capabilities.

geeignet als

• Masterarbeit Kern-, Teilchen- und Astrophysik

Themensteller(in): Allen C. Caldwell

Analysis of time-resolved proton-bunch images in the AWAKE experiment

The AWAKE experiment at CERN is a proof-of-principle experiment to demonstrate electron acceleration in a plasma wakefield generated by a proton bunch.  The main diagnostic of the experiment is a streak camera, which provides time resolved images of the proton and electron bunches.  The student will investigate the limits of resolution achievable with the streak camera using Fourier Transform and other techniques.

geeignet als

• Bachelorarbeit Physik
• Masterarbeit Kern-, Teilchen- und Astrophysik

Themensteller(in): Allen C. Caldwell

Determination of the resolution function of the B0 anti-B0 decay time difference

One of the goals of the Belle II experiment is the study of the CP asymmetries in the

time evolution of the neutral B mesons. A clean laboratory to study the two-state system

of B0 and anti-B0 mesons is provided by the (4S) resonance which can be produced in

e+ e􀀀 annihilation at the center of mass energy of 10.58 GeV. In SuperKEKB, the beam

energies to form the (4S) are chosen asymmetrically in order to translate the decay time

difference into a length: t = l=c, where l is the boost direction. The B0 and anti-B0

produced by the decay of the (4S) cannot oscillate independently before they decay but

are locked in a quantum-entangled state. Thus the identification of one of the B mesons

as a B0 (anti-B0) yields the flavor of the other B meson as anti-B0 (B0) at the same

time. If the anti-B0 (B0) is fully reconstructed to a CP eigenstate, the difference between

the particle and the antiparticle can be studied using the shape of the distribution of

the difference of their decay times. The goal is to determine the experimental resolution

function of the distance (translated to the difference of the decay times) between the

vertices of the two B mesons as a function of the different decay vertex qualities and

vertex detector running conditions.

geeignet als

• Bachelorarbeit Physik
• Masterarbeit Kern-, Teilchen- und Astrophysik

Themensteller(in): Allen C. Caldwell

Evaluation of the neural network z-vertex trigger

The track trigger of the Belle II experiment will include a z-vertex trigger based on neural

networks, whose purpose is to determine the origin of tracks and to suppress background

coming from outside the interaction point of the colliding beams. The commissioning

phase of the experiment, which has started in February 2018, will provide first real data

to evaluate the z-vertex trigger, which has so far only been tested on simulated tracks.

The task is to compare the results of the trigger to the full offline reconstruction and to

measure the resolution of the z-vertex trigger. In addition, the background distribution

has to be analyzed in order to determine a suitable cut for an efficient background

suppression.

geeignet als

• Masterarbeit Kern-, Teilchen- und Astrophysik

Themensteller(in): Allen C. Caldwell

Finetuning of the Gated-Mode operation of the Pixel Vertex Detector

The Belle II experiment is located at the e+e􀀀-collider SuperKEKB at the High Energy

Accelerator Research Organization (KEK) in Japan. Due to the operation mode of the

collider, which aims for a new world record in luminosity, the online injected particle

bunches create a high noise environment for a certain time period. During this time

a normal operation of the Pixel Vertex Detector (PXD) is not possible. However, the

sensitive area of the PXD modules is based on the Depleted P-channel Field Effect

Transistor (DEPFET) technology, which allows an operation mode in which the sensitive

area can be shielded against the noise. The so called “Gated Mode” was already proven

to work on prototype modules in the laboratory. The task is to optimize the “Gated

Mode” and to prepare it for the operation in the running experiment.

geeignet als

• Masterarbeit Kern-, Teilchen- und Astrophysik

Themensteller(in): Allen C. Caldwell

Numerical study of Black-Hole inspired neural net model

A Markov Chain Monte Carlo algorithm (BAT -https://bat.mpp.mpg.de) will be used to study the properties of a neural net model whose properties are defined by analogy to Black Hole physics (arXiv:1711.09079).  The student will investigate the convergence properties and stability of solutions with different algorithms.

geeignet als

• Bachelorarbeit Physik
• Masterarbeit Kern-, Teilchen- und Astrophysik

Themensteller(in): Allen C. Caldwell

Optimization of operating parameters of the Pixel Vertex Detector

The innermost tracking detector of Belle II is the Pixel Vertex Detector (PXD). It consists

of 40 monolithic silicon modules arranged in two layers. The detector is developed and

commissioned by a mostly European driven collaboration. The modules were processed at

the Semiconductor Laboratory of the MPG (Halbleiterlabor - HLL) in Munich. One task

of the Belle II group at the MPP is the testing of prototype modules and characterization

of the final modules. The modules are operated and analyzed with automated scripts

to find the optimal working parameters. It is expected that those settings will change

under the radiation environment during the experiment. The goal is to further develop

the used methods and adapt them for operation at the experiment in Japan.

geeignet als

• Masterarbeit Kern-, Teilchen- und Astrophysik

Themensteller(in): Allen C. Caldwell

Tuning of the cluster selection of the Belle II Pixel Vertex Detector

The main task of the tracking is the reconstruction of charged particles originating from

primary and secondary vertices. Due to the present implementation of the tracking algorithms

it is not possible to use the reconstructed hits of the first layer of the Pixel Vertex

Detector when no hits are available in the second layer, because of the impact of the high

machine background on the first layer. The task is the development of an algorithm for

improving the separation power between the clusters coming from interesting tracks and

the ones coming from the machine background.

geeignet als

• Bachelorarbeit Physik
• Masterarbeit Kern-, Teilchen- und Astrophysik

Themensteller(in): Allen C. Caldwell