Difference between revisions of "Master student Projects"

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=== Projects for Master students in the Nikhef ATLAS group ===
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=== Projects for Master students in the Nikhef B-physics (LHCb) group 2020 - 2021 ===
  
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date: August 2013
+
date: April 2020
  
−
This is an overview with all available Master student projects in the Nikhef ATLAS group.
+
This is an overview with all available Master student projects in the Nikhef B-physics (LHCb) group.
  
  
−
If you have your own research proposal, need more detailed information on the (availability) of individual proposals or would like to discuss about other available projects in the group you are always welcome to contact
+
If you have your own research proposal, need more detailed information on the  
−
either the contact person for the project and/or the Nikhef ATLAS group leaders:
+
(availability) of individual proposals or would like to discuss about other available  
 +
projects in the group you are always welcome to contact
 +
either the contact person for the project and/or the Nikhef B-physics group leader:
  
−
Stan Bentvelsen ___ [''' E-mail: stanb_at_nikhef.nl''', Tel 020-5925140, Nikhef room H250]
+
Marcel Merk [e-mail: i93_at_nikhef.nl, Tel 020-5925107, Nikhef room N243]
  
−
Paul de Jong ______ [''' E-mail: h26_at_nikhef.nl''', Tel 020-5922087, Nikhef room H253]
+
For an overview of the theses written in the Nikhef B-physics group you can look at the
 +
[https://wiki.nikhef.nl/lhcb/Thesis_page_LHCb_Nikhef Nikhef LHCb theses page]
  
 +
(The full list of projects at Nikhef can be found [https://wiki.nikhef.nl/education/Master_Projects here].)
  
−
For an overview of the theses written in the Nikhef ATLAS group you can look at the
+
=== Master projects in the Nikhef B-physics group ===
−
[http://www.nikhef.nl/pub/experiments/atlaswiki/index.php/Thesis_page_ATLAS_Nikhef Nikhef ATLAS group theses page]
 
  
 +
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TEMPLATE
  
 +
{| border="1" cellpadding="2" cellspacing="0"
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|-
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! style="background:#3399ff;" | <font color=#ffffff> 1) Title </font>
 +
|}
 +
 +
'''Supervisor''' : S.Taff (staff)
 +
 +
'''Research Description:'''
 +
 +
Abstract
 +
 +
''' Relevant information: '''
 +
 +
[1]  [https://arxiv.org/abs/1507.03414 arXiv:1507.03414] (thesis or paper)
 +
 +
END TEMPLATE
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##########################################################################  -->
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 +
{| border="1" cellpadding="2" cellspacing="0"
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|-
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! style="background:#3399ff;" | <font color=#ffffff> 1) Measurement of delta md </font>
 +
|}
 +
 +
'''Supervisor''' : Niels Tuning (staff), Emmy Gabriel (postdoc), Michele Veronesi (PhD)
 +
 +
'''Research Description:'''
 +
 +
The decay B0->D-pi+ is very abundant in LHCb, and therefore ideal to study the oscillation frequency
 +
delta md, with which B0 mesons oscillate into anti-B0 mesons, and vice versa.
 +
This process proceeds through a so-called box diagram which might hide new yet-undiscovered particles.
 +
Recently, it has been realized that value of delta md is in tension with the valu of CKM-angle gamma,
 +
triggering renewed interest in this measurement.
 +
 +
Our group at Nikhef has 10 years experience in the analysis of B->Dh decays.
 +
This analysis may lead to a publication on behalf of the LHCb collaboration.
 +
 +
''' Relevant information: '''
 +
 +
 +
[1] [https://arxiv.org/abs/1812.06963 arXiv:1812.06963] M. Blanke, A. Buras, Emerging delta md Anomaly from Tree-Level Determinations of |Vcb| and the angle gamma
 +
 +
[2] [https://arxiv.org/abs/1911.07856 arXiv:1911.07856] D. King, A. Lenz, Th. Rauh, |Vcb| and gamma from mixing
 +
 +
[3] [https://indico.nikhef.nl/event/1379/contribution/1/material/slides/0.pdf talk] N. Tuning, CKM unitarity and B mixing
 +
 +
[4]  [https://arxiv.org/abs/1210.6750 arXiv:1210.6750] LHCb coll.,
 +
 +
 +
[5] [https://arxiv.org/abs/1805.03448 arXiv:1805.03448] LHCb coll.,
 +
 +
 +
 +
{| border="1" cellpadding="2" cellspacing="0"
 +
|-
 +
! style="background:#3399ff;" | <font color=#ffffff> 2) Searching for CPT violation </font>
 +
|}
 +
 +
'''Supervisor''' : Niels Tuning (staff), Emmy Gabriel (postdoc), Michele Veronesi (PhD)
 +
 +
'''Research Description:'''
 +
 +
CPT symmetry is closely linked to Lorentz symmetry, and any violation
 +
would revolutionize science. There are possibilities though that supergravity could
 +
cause CPT violating effects in the system of neutral mesons.
 +
The precise study of B0s oscillations in the abundant Bs->Dspi decays can
 +
give the most stringent limits on Im(z) to date.
 +
 +
Our group at Nikhef has 10 years experience in the analysis of B->Dh decays.
 +
This analysis may lead to a publication on behalf of the LHCb collaboration.
 +
 +
''' Relevant information: '''
 +
 +
[1]  [https://arxiv.org/abs/1603.04804 arXiv:1603.04804] LHCb coll.,
 +
Search for violations of Lorentz invariance and CPT symmetry in B0(s) mixing
 +
 +
[2] [https://arxiv.org/abs/1407.1269 arXiv:1407.1269] J. van Tilburg and M. van Veghel,
 +
Status and prospects for CPT and Lorentz invariance violation searches in neutral meson mixing
 +
 +
 +
{| border="1" cellpadding="2" cellspacing="0"
 +
|-
 +
! style="background:#3399ff;" | <font color=#ffffff> 3) BR(B0->D-pi+) and fd/fu with B+->D0pi+ </font>
 +
|}
 +
 +
'''Supervisor''' : Niels Tuning (staff), Emmy Gabriel (postdoc), Michele Veronesi (PhD)
 +
 +
'''Research Description:'''
 +
 +
The abundant decay B0->D-pi+ is often used as normalization channel, given its
 +
clean signal, and well-known branching fraction, as measured by the B-factories.
 +
However, this branching fraction can be determined more precisely, when comparing
 +
to the decay B+->D0pi+ , which has a twice better precision.
 +
 +
In addition, the production of B0 and B+ mesons is often assumed to be equal,
 +
based on isospin symmetry. The study of B+->D0pi+ and B0->D-pi+ allows for the
 +
first measurement of this ratio, fd/fu.
 +
 +
Our group at Nikhef has 10 years experience in the analysis of B->Dh decays.
 +
This analysis may lead to a publication on behalf of the LHCb collaboration.
 +
 +
''' Relevant information: '''
 +
 +
[1]  [https://cds.cern.ch/record/2636716/files/CERN-THESIS-2018-137.pdf CERN-THESIS-2018-137] J. Butter,
 +
Branching fraction measurement of B0->D+s pi?
 +
 +
 +
 +
{| border="1" cellpadding="2" cellspacing="0"
 +
|-
 +
! style="background:#3399ff;" | <font color=#ffffff> 5) Searches for new pentaquarks </font>
 +
|}
 +
 +
'''Supervisor''' : P. Koppenburg (staff)
 +
 +
'''Research Description:'''
 +
 +
In 2015 LHCb surprisingly discovered states containing five quarks, called Pc+ pentaquarks. Such particles question our understanding of confinement, the principle that forces quarks to remain in a single hadron. Which hadrons are allowed and which are not? The pentaquarks were found in the decay of the Lambda_b baryon to a Pc+ and a kaon, and Pc+ to a J/psi and a proton. This project aims at studying other similar but yet unobserved decays which could reveal the presence of the know Pc+, or yet unknown pentaquarks. The student will optimise a selection for finding such a decay in LHCb data using machine learning techniques.
 +
 +
''' Relevant information: '''
 +
 +
[1]  [https://arxiv.org/abs/1507.03414 arXiv:1507.03414] (the pentaquark paper)
 +
 +
[2] [https://arxiv.org/abs/1406.0755 arXiv:1406.0755] (a paper by P. Koppenburg similar to what the project could lead to).
 +
 +
 +
{| border="1" cellpadding="2" cellspacing="0"
 +
|-
 +
! style="background:#3399ff;" | <font color=#ffffff> 6) Measurement of the relative efficiency of muons and electrons with J/psi->ll decays </font>
 +
|}
 +
 +
''' Supervisors:''' Patrick Koppenburg
 +
 +
''' Research description: '''
 +
 +
LHCb has produced intriguing results hinting at violation of lepton universality. As extraordinary claims require extraordinary evidence we propose to perform a measurement of the relative reconstruction efficiency of electrons and muons by comparing the number of J/psi particles counted in the di-electron and di-muon final states.
 +
 +
 +
 +
{| border="1" cellpadding="2" cellspacing="0"
 +
|-
 +
! style="background:#3399ff;" | <font color=#ffffff> 7) Very rare decays of B mesons</font>
 +
|}
 +
 +
''' Supervisors:''' Marcel Merk
 +
 +
''' Research description: '''
 +
Decays of B-mesons to a pair of muons or a pair of electrons are very strongly suppressed in the Standard Model. As a consequence these decays are sensitive to virtual contributions of particles beyond the Standard Model. The project includes a theoretical study on these sensitivties and/or experimental improvements to the measurement. 
 +
 +
 +
 +
{| border="1" cellpadding="2" cellspacing="0"
 +
|-
 +
! style="background:#3399ff;" | <font color=#ffffff> 8) Measurement of Central Exclusive Production Rates of Chi_c using converted photons in LHCb. </font>
 +
|}
 +
 +
''' Supervisor:''' Kazu Akiba
 +
 +
''' Research description: '''
 +
Central exclusive production (CEP) of particles at the LHC is characterised by a extremely clean signature.  Differently from the typical inelastic collisions where many particles are created resulting in a so-called Primary Vertex, CEP events have only the final state particles of interest. In this project the particle of interest is a pair of charmed quarks creating a chi_c particle. In theory this process is generated by a long range gluon exchange and can elucidate the nature of the strong force, described by the quantum chromodynamics in the the standard model. The proposed work involves  analysing a pre-existing dataset with reconstructed chi_c and simulating events at the LHCb in order to obtain the relative occurrence rate of each chi_c species (spins 0, 1, 2), a quantity that can be easily compared to theoretical predictions.
 +
 +
{| border="1" cellpadding="2" cellspacing="0"
 +
|-
 +
! style="background:#3399ff;" | <font color=#ffffff> 9) Optimization studies for Vertex detector at the High Lumi LHCb </font>
 +
|}
 +
 +
''' Supervisor:''' Kazu Akiba
 +
 +
''' Research description: '''
 +
The LHCb experiment is dedicated to measure tiny differences between matter and antimatter through the precise study of rare processes involving b or c quarks.  The LHCb detector will undergo a major modification in order to dramatically increase the luminosity and be able to  measure indirect effects of physics beyond the standard model.  In this environment, over 42 simultaneous collisions are expected to happen at a time interval of 200 ps where the two proton bunches overlap. The particles of interest have a relatively long lifetime and therefore the best way to distinguish them from the background collisions is through the precise reconstruction of displaced vertices and pointing directions.  The new detector considers using extremely recent or even future technologies to measure space (with resolutions below 10 um) and time (100 ps or better) to efficiently reconstruct the events of interest for physics.  The project involves changing completely  the LHCb Vertex Locator (VELO) design in simulation and determine what can be the best performance for the upgraded detector, considering different spatial and temporal resolutions.
 +
 +
 +
{| border="1" cellpadding="2" cellspacing="0"
 +
|-
 +
! style="background:#3399ff;" | <font color=#ffffff> 10) Measurement of charge multiplication in heavily irradiated sensors </font>
 +
|}
 +
 +
''' Supervisor:''' Kazu Akiba
 +
 +
''' Research description: '''
 +
During the R&D phase for the LHCb VELO Upgrade detector a few sensor prototypes were irradiated to the extreme fluence expected to be achieved during the detector lifetime. These samples were tested using high energy particles at the SPS facility at CERN with their trajectories reconstructed by the Timepix3 telescope. A preliminary analysis revealed that at the highest irradiation levels the amount of signal observed is higher than expected, and even larger than the signal obtained at lower doses.  At the Device Under Test (DUT) position inside the telescope, the spatial resolution attained by this system is below 2 um. This means that a detailed analysis can be performed in order to study where and how this signal amplification happens within  the 55x55 um^2 pixel cell.  This project involves analysing the telescope and DUT data to investigate the charge multiplication mechanism at the microscopic level.
 +
 +
 +
{| border="1" cellpadding="2" cellspacing="0"
 +
|-
 +
! style="background:#3399ff;" | <font color=#ffffff> 11) Searching for lepton-universality violation with ?b ? ?l+l? decays </font>
 +
|}
 +
 +
'''Supervisor''' : Niels Tuning (staff), Lex Greeven (PhD), Mick Mulder (postdoc@CERN)
 +
 +
'''Research Description:'''
 +
 +
into muons and into electrons/taus. Recent measurements in meson modes show hints (2 ? 3?) of lepton non-universality. Baryonic modes, however, have been less studied and provide an independent test of lepton-universality. At Nikhef, we study the decay ?b ? ?l+l- , where l can be an electron or a muon. There are two possible project topics:
 +
 +
1. Identifying novel analysis techniques in the high di-lepton invariant mass region. Electrons in this region undergo more Bremsstrahlung, and therefore have a worse momentum resolution,
 +
meaning background from the resonant ? (2s) mode can leak into our signal. Since we expect most of our signal in this region, it is important to improve this, most likely using machine learning techniques.
 +
 +
2. Identifying, simulating, and setting up a rejection for partially reconstructed ?0b ? ?*l+l? backgrounds. By not fully reconstructing the excited ?0, we can mis-reconstruct it as a signal
 +
candidate. Machine learning techniques could be explored.
 +
 +
 +
''' Relevant information: '''
 +
 +
[1]  [https://arxiv.org/abs/1903.09252 arXiv:1903.09252] LHCb coll., Search for lepton-universality violation in B+?K+l+l?decays
 +
 +
[2]  [https://arxiv.org/abs/1705.05802 arXiv:1903.09252] LHCb coll., Test of lepton universality with B0?K*0l+l? decays
 +
 +
[3]  [https://arxiv.org/abs/1912.08139 arXiv:1912.08139] LHCb coll., Test of lepton universality with ?b?pKl+l? decays
 +
 +
[4]  [https://arxiv.org/abs/1602.01399 arXiv:1602.01399] W. Detmold and S. Meinel, ?b??l+l? form factors, differential branching fraction, and angular observables from lattice QCD with relativistic b-quarks
 +
 +
 +
 +
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<!--
 +
=============
 +
OLD PROJECTS
 +
==============
 +
-->
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<!--
 +
| border="1" cellpadding="2" cellspacing="0"
 +
|-
 +
! style="background:#3399ff;" | <font color=#ffffff> 5) A Scintillator Fibers Tracker </font>
 +
|}
 +
''' Supervisors:''' Antonio Pellegrino
 +
''' Research description: '''
 +
The LHCb collaboration is upgrading the present tracking system
 +
constructing a new tracker based on scintillating fibers combined
 +
with silicon photo-multipliers (SiPM): the SciFi Tracker!
 +
Nikhef plays a key role in the project, as we will build the
 +
SciFi fibers modules, the cold-box enclosure housing the SiPMs,
 +
and a large part of the on-detector electronics. In all these
 +
areas, interesting test hardware and software has to be realized,
 +
and several research topics for a Master project are available,
 +
taking the student in contact with state-of-the-art particle detectors,
 +
in a large team of physicists and engineers. Possible collaborations
 +
with the Nikhef R&D group can also be envisaged.
 +
-->
 +
<!-- ################################################# -->
  
  
 +
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 +
<!--
 +
{| border="1" cellpadding="2" cellspacing="0"
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|-
 +
! style="background:#3399ff;" | <font color=#ffffff> 7) Construction of the velo upgrade detector</font>
 +
|}
 +
''' Supervisors:''' Wouter Hulsbergen
 +
''' Research description: '''
 +
  
 +
{| border="1" cellpadding="2" cellspacing="0"
 +
|-
 +
! style="background:#3399ff;" | <font color=#ffffff> 8) *Probing the dark sector with Y(1S)->4mu events* </font>
 +
|}
 +
''' Supervisors:''' Wouter Hulsbergen
 +
''' Research description: '''
 +
In certain parts of their parameter space Hidden Valley theories predict upsilon decays to two new dark sector particles that subsequently decay into two muons. These particles may or may not be long-lived. In this project we search for such events in LHCb run-2 data using the Turbo stream.
  
−
=== Master projects in the Nikhef ATLAS group ===
 
  
 
{| border="1" cellpadding="2" cellspacing="0"
 
{| border="1" cellpadding="2" cellspacing="0"
 
|-
 
|-
−
! style="background:#3399ff;" | <font color=#ffffff> 1) The polarisation of single top quarks at the LHC </font>
+
! style="background:#3399ff;" | <font color=#ffffff> 6) The Z forward backward asymmetry </font>
 +
|}
 +
''' Supervisors:''' Wouter Hulsbergen
 +
''' Research description: '''
 +
The forward backward asymmetry of Z->mumu decays probes the standard model weak mixing angle, providing a strong test of the standard model. A dominating systematic uncertainty in this measurement is the affect of detector misalignments. In this project Z->mumu events are used to improve the detector alignment and thereby increase the precision of the run-2 measurements.
 +
 
 +
 
 +
-->
 +
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 +
 
 +
 
 +
<!-- ################################################# -->
 +
<!--
 +
{| border="1" cellpadding="2" cellspacing="0"
 +
|-
 +
! style="background:#3399ff;" | <font color=#ffffff> 4) A search for heavy neutrinos in the decay of W at LHCb  </font>
 +
|}
 +
''' Supervisors:''' Wouter Hulsbergen (staff), Elena Dall'Occo (PhD)
 +
''' Research description: '''
 +
 
 +
Neutrinos are arguably the most mysterious of all known fundamental fermions as they are both much lighter than all others and only weakly interacting.
 +
It is thought that the tiny mass of neutrinos can be explained by their mixing with so-far unknown, much heavier, neutrino-like particles.
 +
In this research proposal we look for these new neutrinos in the decay of the SM W-boson using data with the LHCb experiment at CERN.
 +
The W boson is assumed to decay to a heavy neutrino and a muon. The heavy neutrino subsequently decays to a muon and a pair of quarks.
 +
Both like-sign and opposite-sign muon pairs will be studied. The result of the analysis will either be a limit on the production of the new neutrinos
 +
or the discovery of something entirely new.
 +
-->
 +
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 +
 
 +
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 +
<!-- Commented out by Niels Apr 2020.
 +
 
 +
{| border="1" cellpadding="2" cellspacing="0"
 +
|-
 +
! style="background:#3399ff;" | <font color=#ffffff> 2) Measurement of BR(B0 -> Ds+ Ds-) </font>
 +
|}
 +
''' Supervisors:''' Sevda Esen (postdoc), Niels Tuning (staf), Michele Veronesi (PhD)
 +
''' Research description: '''
 +
 
 +
This project aims to discover the branching fraction of the decay B0->Ds- Ds+.
 +
The decay B0->Ds- Ds+ is quite rare, because it occurs through the exchange of a W-boson between the
 +
b and the d-quark of the B0-meson.
 +
This decay proceeds via Cabibbo-suppressed W-exchange and
 +
has not yet been observed; theoretical calculations predict
 +
a branching fraction at the order of 10^-5 with a best
 +
experimental upper limit of 3.6x10^-5.
 +
 
 +
A measurement of the decay rate of B0 ->  Ds+Ds- relative to
 +
that of B0 -> D+D- can provide an estimate of the W-exchange contribution
 +
to the latter decay, a crucial piece of information for extracting
 +
the CKM angle gamma from B0 -> D(*)D(*).
 +
 
 +
The aim is to determine the relative branching fraction of  B0->Ds+Ds- with respect to B0->Ds+D- decays
 +
(which has the best known branching ratio at present, (7.2 +- 0.8)x10^-3),
 +
in close collaboration with the PhD.
 +
The aim is that this project results in a journal publication on behalf of the LHCb collaboration.
 +
For this project computer skills are needed.
 +
The ROOT programme and C++ and/or Python macros are used.
 +
This is a project that is closely related to previous analyses in the group.
 +
Weekly video meetings with CERN coordinate the efforts with in the LHCb collaboration.
 +
 
 +
''' Relevant information: '''
 +
 
 +
[1] M.Jung and S.Schacht,
 +
"Standard Model Predictions and New Physics Sensitivity in B -> DD Decays"
 +
https://arxiv.org/pdf/1410.8396.pdf
 +
[2] L.Bel, K.de Bruyn, R. Fleischer, M.Mulder, N.Tuning,
 +
"Anatomy of B -> DD Decays"
 +
https://arxiv.org/pdf/1505.01361.pdf
 +
[3] A.Zupanc et al [Belle Collaboration]
 +
"Improved measurement of B0 -> DsD+ and search for B0 -> Ds+Ds at Belle"
 +
https://arxiv.org/pdf/hep-ex/0703040.pdf
 +
[4] B.Aubert et al. [Babar Collaboration]
 +
"Search for the W-exchange decays B0 -> DD+"
 +
https://arxiv.org/pdf/hep-ex/0510051.pdf
 +
[5] R.Aaij et al. [LHCb Collaboration],
 +
"First observations of B0s -> D+D, Ds+D and D0D0 decays"
 +
https://arxiv.org/pdf/1302.5854.pdf
 +
 
 +
 
 +
{| border="1" cellpadding="2" cellspacing="0"
 +
|-
 +
! style="background:#3399ff;" | <font color=#ffffff> 3) Measurement of relative ratio of B+ -> D0D+ and B+ -> D0Ds decays </font>  
 
|}
 
|}
 +
''' Supervisors:''' Sevda Esen (postdoc), Niels Tuning (staf), Michele Veronesi (PhD)
 +
''' Research description: '''
 +
 +
This decay is closely related to B0->Ds- Ds+ (see above), and close collaboration between the two master projects is foreseen.
 +
The decay mode B+->D0D+ is expected to be dominated by tree diagrams with some additional
 +
contributions from penguin diagrams. Assuming SU(3) symmetry,
 +
measurement of its branching fraction relative to Cabibbo-favored
 +
B+->D0D will enable better understanding of penguin contributions
 +
to the CP violating mixing phase.
 +
 +
''' Relevant information: '''
 +
 +
[1] L.Bel, K.de Bruyn, R. Fleischer, M.Mulder, N.Tuning,
 +
"Anatomy of B -> DD Decays"
 +
https://arxiv.org/pdf/1505.01361.pdf
 +
[2] R.Aaij et al. [LHCb Collaboration],
 +
"First observations of B0s -> D+D, Ds+D and D0D0 decays"
 +
https://arxiv.org/pdf/1302.5854.pdf
 +
[3] PDG: http://pdglive.lbl.gov/BranchingRatio.action?desig=261&parCode=S041
  
 +
-->
 +
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−
''' Supervisors:''' Marcel Vreeswijk (staf) and Rogier van der Geer (PhD student)
+
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 +
<!-- Commented out Nov 2014 by Niels (Elise is on this project)
  
 +
{| border="1" cellpadding="2" cellspacing="0"
 +
|-
 +
! style="background:#3399ff;" | <font color=#ffffff> 1) Study of long-living particles </font>
 +
|}
  
 +
''' Supervisors:''' Wouter Hulsbergen (staf) and Veerle Heijne (PhD)
 
''' Research description: '''
 
''' Research description: '''
  
−
Single top quark production is a rare process which is only in reach of the Tevatron-collider and
+
Supersymmetry is potentially the key to understand the Dark Matter in the Universe.
−
the Large Hadron Collider since the last decade. The cross section for t-channel top quark
+
Within the SUSY framework, long-living supersymmetric particles can exist, which
−
production at the LHC allows precision measurements of the spin structure of the Wtb vertex as a
+
can be detected by the LHCb detector. The search for these particles will be performed on
−
probe for new physics. For this research the data recorded with the ATLAS detector at 8TeV will be
+
the recent data set recorded in 2012, and some work is also needed on the trigger selection,
−
used. The observables consist of the decay angles of the top quark from which (anomalous) couplings
+
to prepare for data taking in 2015, when the LHC will be running at a higher center-of-mass energy.
−
can be extracted. Several contributions to the research are possible, which involve:
 
−
-selection of events and reconstruction of the observables;
 
−
-unfolding techniques from measured distribution to the underlying truth distribution;
 
−
-which quantities can be extracted from the distribution and how do these translate to general
 
−
couplings?
 
  
−
For this project you need to have affinity with quantum mechanics and computer skills are needed.
+
For this project computer skills are needed.
 
The ROOT programme and C++ and/or Python macros are used. You become part of our research group
 
The ROOT programme and C++ and/or Python macros are used. You become part of our research group
−
(~5 persons); we have weekly meetings with colleagues at CERN and depending on the results -and
+
(~5 persons); we have weekly video meetings with colleagues at CERN.
−
perhaps some luck- you may co-author an (internal ATLAS) research note. The project will be soon
+
 
−
at full pace, requiring you to be flexible.
+
''' Relevant information: '''
 +
Master thesis Suzanne Klaver (2013):
 +
[http://www.nikhef.nl/pub/experiments/bfys/lhcb/Theses/master/2013_SuzanneKlaver.pdf A Search for Long-lived Neutralinos in LHCb]
 +
 
 +
End comment Niels Nov 2014 -->
 +
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 +
 
 +
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 +
<!-- Commented out July 2014 Niels
 +
 
 +
{| border="1" cellpadding="2" cellspacing="0" |- ! style="background:#3399ff;" | <font color=#ffffff>
 +
2) World's best measurement of the Bc+ mass with Bc+ -> Bs pi+
 +
</font>|}
 +
''' Supervisors:''' Niels Tuning (staf), Jacco de Vries (PhD)
 +
''' Research description: '''
 +
 
 +
At Nikhef we recently discovered the first weak B-decay with another B-to-B decay: Bc+ -> Bs pi+.
 +
The mass difference between the Bc+ and Bs meson is very small (only about 0.9 GeV), and as
 +
a result the mass difference can be accurately determined. This will lead to the world's best
 +
measurement of the Bc+ mass.
 +
 +
A theoretical component (in collaboration with Robert Fleischer) can be added to this project,
 +
by examining the various possible Bc+ decay modes, and make quantitative predictions for the
 +
relative branching fractions. Investigating the various decay modes, can lead to a method
 +
for determining the absolute production rate of Bc+ mesons at the LHC, which is at present still unknown.
 +
 +
For this project computer skills are needed.
 +
The ROOT programme and C++ and/or Python macros are used.
 +
This is a small project, where the student can perform his research in an independent way.
 +
The group at Nikhef (~2 persons) collaborates with a small group at CERN that studies the
 +
same decay, but with a different Bs final state.
 +
This research will likely result in an official LHCb publication.
 +
 
 +
''' Relevant information: '''
 +
 +
[1] Master thesis Jacco de Vries (2013):
 +
[http://www.nikhef.nl/pub/experiments/bfys/lhcb/Theses/maste/2013_JaccoDeVries.pdf First observation of the decay Bc+ -> B0s pi+]
 +
 +
[2] LHCb collaboration, arXiv:1308.4544 (2013): [http://arxiv.org/abs/1308.4544 Observation of the decay Bc+ -> Bs pi+]
 +
 
 +
[3] R. Fleischer, N. Serra and N. Tuning, Phys. Rev. D 83, 014017 (2011)
 +
[http://arxiv.org/abs/arXiv:1012.2784 Tests of Factorization and SU(3) Relations in B Decays into Heavy-Light Final States]
 +
 
 +
End comment Niels Jul 2014-->
 +
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 +
 
 +
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 +
<!-- Commented out 2014 Marcel
 +
{| border="1" cellpadding="2" cellspacing="0"
 +
|-
 +
! style="background:#3399ff;" | <font color=#ffffff> 2) Light Higgs search A0 -> mu+mu- </font>
 +
|}
 +
''' Supervisors:''' Wouter Hulsbergen (staf), Pieter David (PhD)
 +
''' Research description: '''
 +
Supersymmetry is potentially the key to understand the Dark Matter in the Universe.
 +
In supersymmetry, there is not just one Higgs boson as in the Standard Model,
 +
but there ar five Higgs bosons. Certain SUSY models predict a relatively light A0 Higgs particle.
 +
The A0 particle can decay to two muons, which would be clearly detectable at LHCb
 +
thanks to its excellent mass resolution, leading to a narrow mass peak in the di-muon invariant mass spectrum.
 +
 
 +
For this project computer skills are needed.
 +
The ROOT programme and C++ and/or Python macros are used.
 +
This is a new project, within the small group at Nikhef (~3 persons). The analysis resembles the search for the
 +
decay Bs->mu+mu-, which was discovered this Summer and led to a lot of attention.
 +
 
 +
''' Relevant information: '''
 +
LHCb collaboration, arXiv:1307.5024
 +
[http://arxiv.org/pdf/1307.5024.pdf Measurement of the B0s->mu+mu- branching fraction and search for B0->mu+mu- decays at the LHCb experiment]
 +
 
 +
End comment Marcel -->
 +
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 +
 
 +
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 +
<!-- Commented out Marcel 2014
 +
{| border="1" cellpadding="2" cellspacing="0"
 +
|-
 +
! style="background:#3399ff;" | <font color=#ffffff> 3) Understanding 'penguin pollution' in phi_s with Bs -> J/psi K* decays </font>
 +
|}
 +
 
 +
''' Supervisors:''' Gerhard Raven (staf), Vasilis Syropoulos (PhD)
 +
''' Research description: '''
 +
 
 +
The measurement of the CP-violating phase phi_s is a flagship in LHCb.
 +
A deviating measurement of phi_s can be a hint of new particles, and can
 +
shed light on the mystery why we live in a matter-dominated Universe without anti-matter.
 +
However, certain decay diagrams (called 'penguin' diagrams) can affect the
 +
measurement of phi_s, which is theoretically difficult to quantify.
 +
To solve this problem, measurements on the decay Bs->J/psiK* will provide important
 +
constraints on these penguin contributions.
 +
 
 +
For this project computer skills are needed.
 +
The ROOT programme and C++ and/or Python macros are used.
 +
This is a project that is closely related to the larger effort at Nikhef (~5 people) of measuring phi_s with
 +
Bs->J/psiPhi decays. Weekly video meetings with CERN coordinate the efforts within the LHCb collaboration.
 +
 
 +
''' Relevant information: '''
 +
 
 +
LHCb collaboration, arXiv:1304.2600,
 +
[http://arxiv.org/pdf/1304.2600.pdf Measurement of CP-violation and the Bs0-meson decay width difference with Bs0->J/psiK+K- and Bs0->J/psi pi+pi- decays]
 +
 
 +
End comment Marcel -->
 +
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 +
 
 +
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 +
<!-- Commented out Nov 2014 by Niels (Georgios is on this project)
 +
 
 +
{| border="1" cellpadding="2" cellspacing="0"
 +
|-
 +
! style="background:#3399ff;" | <font color=#ffffff> 2) Searching for Lorentz Invariance Violation with Bs -> J/psi phi decays </font>
 +
|}
 +
''' Supervisors:''' Gerhard Raven (staf), Jeroen van Tilburg (Postdoc)
 +
''' Research description: '''
 +
 
 +
The measurement of CP violation occurring in decays of the type Bs->J/psi phi is a flagship analysis in the LHCb experiment. However, no-one in LHCb has tested whether CPT symmetry is violated. CPT symmetry is tightly connected to the principle of Lorentz invariance. Lorentz invariantz violation would become visible if the decay rate would show any dependency to a fixed direction in space. In this project the CP violation analysis is extended to test for Lorentz Invariance violation.
 +
 +
For this project computer skills are needed.
 +
The ROOT programme and C++ and/or Python macros are used.
 +
This is a project that is closely related to the larger effort at Nikhef (~5 people) of measuring phi_s with
 +
Bs->J/psiPhi decays. Weekly video meetings with CERN coordinate the efforts within the LHCb collaboration.
 +
 
 +
''' Relevant information: '''
 +
Belle Collaboration: arXiv:1203.0930v2,
 +
[http://arxiv.org/pdf/1203.0930.pdf  Search for Time-Dependent CPT Violation in Hadronic and Semileptonic B Decays]
 +
 
 +
End comment Niels Nov 2014 -->
 +
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 +
 
 +
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 +
<!-- Comment Marcel 2014
 +
{| border="1" cellpadding="2" cellspacing="0"
 +
|-
 +
! style="background:#3399ff;" | <font color=#ffffff> 5) Search for a light Higgs in the decay Sigma+ -> p mu mu </font>
 +
|}
 +
 
 +
''' Supervisors:''' Francesco Dettori (postdoc), Antonio Pellegrino (staf), Siim Tolk (PhD)
 +
''' Research description: '''
 +
The decay Sigma+ -> p mu mu is very rare in the Standard Model. In 2005 the
 +
HyperCP experiment has seen first evidence of this decay, but with a very peculiar
 +
feature:  all the three observed events have the same di-muon invariant mass... This
 +
could be due to new particles (a very light Higgs?) in the decay of the type
 +
Sigma+ -> p X decay, with X a new particle decaying into two muons.
 +
The search for this decay at LHCb is important both to confirm this very rare
 +
process and to search for possible new phenomena.
 +
 
 +
For this project computer skills are needed. The ROOT programme and C++ and/or
 +
Python macros are used. This is a small project, where the student can perform
 +
his research in an independent way.
 +
This research will likely result in an official LHCb publication.
 +
 
 +
''' Relevant information: '''
 +
 
 +
[1] HyperCP Collaboration, Phys. Rev. Lett. 94, 021801 (2005)
 +
[http://arxiv.org/abs/hep-ex/0501014 Evidence for the decay Sigma+ -> p mu mu]
 +
[2] X.-G. He, J. Tandean, G. Valencia, Phys. Rev. Lett. 98, 081802 (2007)
 +
[http://arxiv.org/abs/hep-ph/0610362 Has HyperCP Observed a Light Higgs Boson?]
 +
 
 +
End comment Marcel -->
 +
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 +
 
 +
<!-- ################################################# -->
 +
<!-- Commented out Marcel April 2016
 +
 
 +
{| border="1" cellpadding="2" cellspacing="0"
 +
|-
 +
! style="background:#3399ff;" | <font color=#ffffff> 1) Bs->mumu and Bd->mumu normalization and B mesons hadronization probabilities </font>
 +
|}
 +
''' Supervisors:''' Antonio Pellegrino (staff), Maarten van Veghel (PhD)
 +
''' Research description: '''
 +
 
 +
The measurement of the Bs-> mu mu and Bd->mu mu decays
 +
is one of the flagships of the LHCb experiment, the latest result in
 +
combination with CMS has recently been published on Nature.
 +
The aim of this project is to study one of the main uncertainties in the
 +
measurements of the branching fractions by measuring the yields of other decays
 +
with a J/Psi in the final state, like B+ -> J/Psi K+ and  Bs-> J/Psi Phi,
 +
that can be detected triggering on the muons decay products of the J/Psi.
 +
These yields are a crucial input to obtain the Bs-> mu mu and Bd->mu mu decays
 +
branching fractions as they provide a relative normalization.
 +
Moreover, in order to use Bd decays to normalize the Bs-> mu mu yields
 +
we need to measure the relative probabilities for a b quark to hadronize
 +
into a Bs (f_s) or a Bd (f_d) meson, that can also be obtained from
 +
B+ -> J/Psi K+,  Bs-> J/Psi Phi and Bd-> J/Psi K* decays.
 +
The ratio f_s/f_d is not a constant and is therefore important
 +
to measure it as a function of both the energy in the center of mass
 +
of the pp collision and the B mesons kinematics. The combination
 +
of previous data at 7 and 8 TeV and data at 13 TeV from the LHC 2015 run
 +
will provide us important new insight and is a result worth a journal
 +
publication in his own right.
 +
 
 +
For this project some programming skills are needed (PYTHON or C++).
 +
Some initial knowledge of the ROOT analysis framework is also useful.
 +
The student will perform his research in a group consisting of two seniors and two Ph.D. students
 +
engaged in the study of very rare decays of the B mesons to di-muon final states and the search
 +
for lepton-flavor violating final states (e.g. electron-muon).
 +
 
 +
''' Relevant information: '''
 +
[1] R.Aaij et al. [LHCb Collaboration], ``Measurement of the fragmentation fraction ratio f_s/f_d and its
 +
dependence on B meson kinematics'', JHEP 04 (2013) 001 [arXiv:1301.5286 [hep-ph]].
 +
 
 +
End comment Marcel April 2016 -->
 +
<!-- ################################################# -->
 +
 
 +
 
 +
<!-- ################################################# -->
 +
<!-- Commented out May 2015 by Niels (Siim, Maarten, Mick already on the project)
 +
{| border="1" cellpadding="2" cellspacing="0"
 +
|-
 +
! style="background:#3399ff;" | <font color=#ffffff> 3) Measurement of pt and eta dependence of B0 and Bs0 production </font>
 +
|}
 +
''' Supervisors:''' Niels Tuning (staf), ... ?
 +
''' Research description: '''
 +
The relative production fractions ("fs/fd") of B0 (with quark content bd) and Bs0 (with quark content bs)
 +
mesons is crucial for the determination of the branching fraction of any Bs0 decay at the LHC. The most
 +
prominent example is the decay Bs->mumu that is very sensitive to the existence of new particles.
 +
The most accurate determination of the dependence of fs/fd as a function of the transverse momentum or angle
 +
of the B-meson will use B0s->J/psiPhi and B+->JpsiK+ decays. You will measure this dependence by measuring
 +
the B0s and B yields using the LHCb data from 2011 and 2012.
 +
 
 +
For this project computer skills are needed.
 +
The ROOT programme and C++ and/or Python macros are used.
 +
This is a project that is closely related to three important analyses in the group:
 +
1) Measurements of fs/fd with hadronic Bs->DsPi decays, 2) Search for the rare decay B0->mu+mu- and
 +
3) Time dependent analysis of Bs->J/psiPhi and B0->J/psiK* decays.
 +
Weekly video meetings with CERN coordinate the efforts with in the LHCb collaboration.
 +
 
 +
''' Relevant information: '''
 +
[1] R.Aaij et al. [LHCb Collaboration], ``Measurement of the fragmentation fraction ratio f_s/f_d and its
 +
dependence on B meson kinematics'', JHEP 04 (2013) 001 [arXiv:1301.5286 [hep-ph]].
 +
[2] R.Aaij et al. [LHCb Collaboration], ''Measurement of the B0s??+?? branching fraction and search for
 +
B0??+?? decays at the LHCb experiment'', Phys.Rev.Lett. 111 (2013) 101805  [arXiv:1307.5024 [hep-ph]]
 +
 
 +
End comment Niels May 2015-->
 +
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 +
 
 +
 
 +
<!-- ################################################# -->
 +
<!-- Commented out Marcel April 2016
 +
 
 +
{| border="1" cellpadding="2" cellspacing="0"
 +
|-
 +
! style="background:#3399ff;" | <font color=#ffffff> 3) B meson Production Asymmetries </font>
 +
|}
 +
 
 +
''' Supervisors:''' Jeroen van Tilburg (Vidi Laureate), Jacco de Vries (PhD)
 +
 
 +
''' Research description: '''
 +
 
 +
At the LHC, B0 mesons and anti-B0 mesons are not produced in equal quantities (about 0.5% more B0 mesons than anti-B0 mesons).
 +
This production asymmetry can be measured with semileptonic decays of the type B0 -> D-(*) mu+ nu (and its charge conjugate decay).
 +
The goal of this measurement is to measure the asymmetry as function of the transverse momentum and (pseudo)-rapidity of the B0 (or anti-B0).
 +
This requires to unfold of the observed kinematic distributions.
 +
 
 +
End comment Marcel April 2016 -->
 +
<!-- ################################################# -->
 +
 
 +
<!-- ################################################# -->
 +
<!-- Commented out Marcel April 2016
 +
{| border="1" cellpadding="2" cellspacing="0"
 +
|-
 +
! style="background:#3399ff;" | <font color=#ffffff> 5) Quantum Decoherence </font>
 +
|}
 +
 
 +
''' Supervisors:''' Jeroen can Tilburg (Vidi Laureate)
 +
''' Research description: '''
 +
When two particles are created in an anti-symmetric wave function, the two particles are entangled, even though they may be separated by large distances.
 +
If one of the particles is forced into one state (projection), this determines the other state instantaneously. Several theoretical models,
 +
motivated by quantum gravity effects, predict the existance of a decoherence parameter. Using decays of phi->K_S K_L,  
 +
it is possible to measure this decoherence parameter by counting the number of phi decays where both neutral kaons are measured as K_S-> pi+ pi-.
 +
If this parameter is measured to be non-zero, it would mean that our current understanding of quantum mechanics is not complete.
 +
 
 +
End Comment Marcel April 2016-->
 +
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Latest revision as of 15:11, 15 February 2021

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