Difference between revisions of "Master student Projects"

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=== Master projects in the Nikhef B-physics group ===
 
=== Master projects in the Nikhef B-physics group ===
  
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TEMPLATE
  
 
{| border="1" cellpadding="2" cellspacing="0"
 
{| border="1" cellpadding="2" cellspacing="0"
 
|-
 
|-
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! style="background:#3399ff;" | <font color=#ffffff> 1) Searches for new pentaquarks </font>
+
! style="background:#3399ff;" | <font color=#ffffff> 1) Title </font>
 
|}
 
|}
  
−
'''Supervisor''' : P. Koppenburg (staff)
+
'''Supervisor''' : S.Taff (staff)
  
 
'''Research Description:'''
 
'''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.
+
Abstract
  
 
''' Relevant information: '''
 
''' Relevant information: '''
  
−
[1]  [https://arxiv.org/abs/1507.03414 arXiv:1507.03414] (the pentaquark paper)
+
[1]  [https://arxiv.org/abs/1507.03414 arXiv:1507.03414] (thesis or paper)
−
 
 
−
[2] [https://arxiv.org/abs/1406.0755 arXiv:1406.0755] (a paper by P. Koppenburg similar to what the project could lead to).
 
  
 +
END TEMPLATE
 +
##########################################################################  -->
  
−
 
+
{| border="1" cellpadding="2" cellspacing="0"
−
 
+
|-
−
{| border="1" cellpadding="2" cellspacing="0"  
+
! style="background:#3399ff;" | <font color=#ffffff> 1) Measurement of delta md </font>
−
|-  
 
−
! style="background:#3399ff;" | <font color=#ffffff> 2) Measurement of BR(B0 -> Ds+ Ds-) </font>  
 
 
|}
 
|}
  
−
''' Supervisors:''' Sevda Esen (postdoc), Niels Tuning (staf), Michele Veronesi (PhD)  
+
'''Supervisor''' : Niels Tuning (staff), Emmy Gabriel (postdoc), Michele Veronesi (PhD)
  
−
''' Research description: '''
+
'''Research Description:'''
  
−
This project aims to discover the branching fraction of the decay B0->Ds- Ds+.
+
The decay B0->D-pi+ is very abundant in LHCb, and therefore ideal to study the oscillation frequency
−
The decay B0->Ds- Ds+ is quite rare, because it occurs through the exchange of a W-boson between the
+
delta md, with which B0 mesons oscillate into anti-B0 mesons, and vice versa.
−
b and the d-quark of the B0-meson.
+
This process proceeds through a so-called box diagram which might hide new yet-undiscovered particles.
−
This decay proceeds via Cabibbo-suppressed W-exchange and
+
Recently, it has been realized that value of delta md is in tension with the valu of CKM-angle gamma,
−
has not yet been observed; theoretical calculations predict
+
triggering renewed interest in this measurement.
−
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  
+
Our group at Nikhef has 10 years experience in the analysis of B->Dh decays.
−
(which has the best known branching ratio at present, (7.2 +- 0.8)x10^-3),
+
This analysis may lead to a publication on behalf of the LHCb collaboration.
−
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: '''
 
''' 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,
+
[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
−
"Anatomy of B -> DD Decays"
 
−
https://arxiv.org/pdf/1505.01361.pdf
 
  
−
[3] A.Zupanc et al [Belle Collaboration]
+
[2] [https://arxiv.org/abs/1911.07856 arXiv:1911.07856] D. King, A. Lenz, Th. Rauh, |Vcb| and gamma from mixing
−
"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]
+
[3] [https://indico.nikhef.nl/event/1379/contribution/1/material/slides/0.pdf talk] N. Tuning, CKM unitarity and B mixing
−
"Search for the W-exchange decays B0 -> DD+"
 
−
https://arxiv.org/pdf/hep-ex/0510051.pdf
 
  
−
[5] R.Aaij et al. [LHCb Collaboration],  
+
[4] [https://arxiv.org/abs/1210.6750 arXiv:1210.6750] LHCb coll.,
−
"First observations of B0s -> D+D, Ds+D and D0D0 decays"
+
Measurement of the B0--B�0 oscillation frequency delta md with the decays B0->D-pi+ and B0->J/psiK*0
−
https://arxiv.org/pdf/1302.5854.pdf
 
  
 +
[5] [https://arxiv.org/abs/1805.03448 arXiv:1805.03448] LHCb coll.,
 +
Measurement of CP violation in B0->D�pi� decays
  
  
−
{| border="1" cellpadding="2" cellspacing="0"  
+
{| 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>  
+
! style="background:#3399ff;" | <font color=#ffffff> 2) Searching for CPT violation </font>
 
|}
 
|}
  
−
''' Supervisors:''' Sevda Esen (postdoc), Niels Tuning (staf), Michele Veronesi (PhD)  
+
'''Supervisor''' : Niels Tuning (staff), Emmy Gabriel (postdoc), Michele Veronesi (PhD)
 +
 
 +
'''Research Description:'''
  
−
''' 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.
  
−
This decay is closely related to B0->Ds- Ds+ (see above), and close collaboration between the two master projects is foreseen.
+
Our group at Nikhef has 10 years experience in the analysis of B->Dh decays.
−
The decay mode B+->D0D+ is expected to be dominated by tree diagrams with some additional
+
This analysis may lead to a publication on behalf of the LHCb collaboration.
−
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: '''
 
''' Relevant information: '''
  
−
[1] L.Bel, K.de Bruyn, R. Fleischer, M.Mulder, N.Tuning,
+
[1] [https://arxiv.org/abs/1603.04804 arXiv:1603.04804] LHCb coll.,
−
"Anatomy of B -> DD Decays"
+
Search for violations of Lorentz invariance and CPT symmetry in B0(s) mixing
−
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
 
−
 
 
−
 
 
−
{| 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)
+
[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
−
''' 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.
 
  
  
 
{| border="1" cellpadding="2" cellspacing="0"
 
{| border="1" cellpadding="2" cellspacing="0"
 
|-
 
|-
−
! style="background:#3399ff;" | <font color=#ffffff> 5) A Scintillator Fibers Tracker </font>
+
! style="background:#3399ff;" | <font color=#ffffff> 3) BR(B0->D-pi+) and fd/fu with B+->D0pi+ </font>
 
|}
 
|}
  
−
''' Supervisors:''' Antonio Pellegrino
+
'''Supervisor''' : Niels Tuning (staff), Emmy Gabriel (postdoc), Michele Veronesi (PhD)
  
−
''' Research description: '''
+
'''Research Description:'''
  
−
The LHCb collaboration is upgrading the present tracking system
+
The abundant decay B0->D-pi+ is often used as normalization channel, given its
−
constructing a new tracker based on scintillating fibers combined
+
clean signal, and well-known branching fraction, as measured by the B-factories.
−
with silicon photo-multipliers (SiPM): the SciFi Tracker!
+
However, this branching fraction can be determined more precisely, when comparing
−
Nikhef plays a key role in the project, as we will build the
+
to the decay B+->D0pi+ , which has a twice better precision.
−
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.
 
  
 +
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.
  
−
{| border="1" cellpadding="2" cellspacing="0"
+
''' Relevant information: '''
−
|-
 
−
! style="background:#3399ff;" | <font color=#ffffff> 6) The Z forward backward asymmetry </font>
 
−
|}
 
  
−
''' Supervisors:''' Wouter Hulsbergen
+
[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?
  
−
''' 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.
 
  
  
 
{| border="1" cellpadding="2" cellspacing="0"
 
{| border="1" cellpadding="2" cellspacing="0"
 
|-
 
|-
−
! style="background:#3399ff;" | <font color=#ffffff> 7) Construction of the velo upgrade detector</font>
+
! style="background:#3399ff;" | <font color=#ffffff> 5) Searches for new pentaquarks </font>
 
|}
 
|}
  
−
''' Supervisors:''' Wouter Hulsbergen
+
'''Supervisor''' : P. Koppenburg (staff)
  
−
''' Research description: '''
+
'''Research Description:'''
  
−
Nikhef contributes to the upgraded LHCb detector (installation 2019-2020) with the construction of vertex detector modules. In this project the student participates in the construction at Nikhef, in particular in R&D studies to determine the optimize the �gluing� process (early 2018), and the analysis of the first test data taken with built modules (spring/summer 2018).
+
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: '''
  
−
{| border="1" cellpadding="2" cellspacing="0"
+
[1]  [https://arxiv.org/abs/1507.03414 arXiv:1507.03414] (the pentaquark paper)
−
|-
 
−
! style="background:#3399ff;" | <font color=#ffffff> 8) *Probing the dark sector with Y(1S)->4mu events* </font>
 
−
|}
 
  
−
''' Supervisors:''' Wouter Hulsbergen
+
[2] [https://arxiv.org/abs/1406.0755 arXiv:1406.0755] (a paper by P. Koppenburg similar to what the project could lead to).
−
 
 
−
''' 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.
 
  
  
 
{| border="1" cellpadding="2" cellspacing="0"
 
{| border="1" cellpadding="2" cellspacing="0"
 
|-
 
|-
−
! style="background:#3399ff;" | <font color=#ffffff> 9) Measurement of the relative efficiency of muons and electrons with J/psi->ll decays </font>
+
! style="background:#3399ff;" | <font color=#ffffff> 6) Measurement of the relative efficiency of muons and electrons with J/psi->ll decays </font>
 
|}
 
|}
  
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{| border="1" cellpadding="2" cellspacing="0"
 
{| border="1" cellpadding="2" cellspacing="0"
 
|-
 
|-
−
! style="background:#3399ff;" | <font color=#ffffff> 10) Very rare decays of B mesons</font>
+
! style="background:#3399ff;" | <font color=#ffffff> 7) Very rare decays of B mesons</font>
 
|}
 
|}
  
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{| border="1" cellpadding="2" cellspacing="0"
 
{| border="1" cellpadding="2" cellspacing="0"
 
|-
 
|-
−
! style="background:#3399ff;" | <font color=#ffffff> 11) Measurement of Central Exclusive Production Rates of Chi_c using converted photons in LHCb. </font>
+
! style="background:#3399ff;" | <font color=#ffffff> 8) Measurement of Central Exclusive Production Rates of Chi_c using converted photons in LHCb. </font>
 
|}
 
|}
  
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{| border="1" cellpadding="2" cellspacing="0"
 
{| border="1" cellpadding="2" cellspacing="0"
 
|-
 
|-
−
! style="background:#3399ff;" | <font color=#ffffff> 12) Optimization studies for Vertex detector at the High Lumi LHCb </font>
+
! style="background:#3399ff;" | <font color=#ffffff> 9) Optimization studies for Vertex detector at the High Lumi LHCb </font>
 
|}
 
|}
  
Line 250: Line 196:
 
{| border="1" cellpadding="2" cellspacing="0"
 
{| border="1" cellpadding="2" cellspacing="0"
 
|-
 
|-
−
! style="background:#3399ff;" | <font color=#ffffff> 13) Measurement of charge multiplication in heavily irradiated sensors </font>
+
! style="background:#3399ff;" | <font color=#ffffff> 10) Measurement of charge multiplication in heavily irradiated sensors </font>
 
|}
 
|}
  
Line 257: Line 203:
 
''' Research description: '''
 
''' 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.
 
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:'''
 +
A current �hot topic� in the field of particle physics is the potential violation of lepton-universality. At the LHCb experiment, lepton-universality tests are performed by looking at the ratio of decays
 +
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
 +
  
  
Line 268: Line 244:
 
OLD PROJECTS  
 
OLD PROJECTS  
 
==============
 
==============
−
  Commented out Nov 2014 by Niels (Elise is on this project)
+
-->
 +
 
 +
<!-- ################################################# -->
 +
<!--
 +
| 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.
 +
-->
 +
<!-- ################################################# -->
 +
 
 +
 
 +
<!-- ################################################# -->
 +
<!--
 +
{| border="1" cellpadding="2" cellspacing="0"
 +
|-
 +
! style="background:#3399ff;" | <font color=#ffffff> 7) Construction of the velo upgrade detector</font>
 +
|}
 +
''' Supervisors:''' Wouter Hulsbergen
 +
''' Research description: '''
 +
Nikhef contributes to the upgraded LHCb detector (installation 2019-2020) with the construction of vertex detector modules. In this project the student participates in the construction at Nikhef, in particular in R&D studies to determine the optimize the �gluing� process (early 2018), and the analysis of the first test data taken with built modules (spring/summer 2018).
 +
 
 +
{| 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.
 +
 
 +
 
 +
{| border="1" cellpadding="2" cellspacing="0"
 +
|-
 +
! 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.
 +
 
 +
 
 +
-->
 +
<!-- ################################################# -->
 +
 
 +
 
 +
<!-- ################################################# -->
 +
<!--
 +
{| 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.
 +
-->
 +
<!-- ################################################# -->
 +
 
 +
<!-- ################################################# -->
 +
<!-- 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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 +
 
 +
<!-- ################################################# -->
 +
<!-- Commented out Nov 2014 by Niels (Elise is on this project)
  
 
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Latest revision as of 13:11, 15 February 2021

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