FCPPL PhD proposals 2015

List of PhD Proposals 2015

1. Optimization of a TPC detector for future e+/e- experiments: Study of distortions dues to space charge and ions feedbacks

Supervisor(s): Roy Aleksan (roy.aleksan@cea.fr), Philippe Schwemling (Philippe.schwenling@cea.fr )

2. Beam halo and Compton process investigation using single crystal chemical vapour deposition diamond sensors at the ATF2 and PHIL electron beam lines

Supervisor(s): Philip Bambade (bambade@lal.in2p3.fr)

3. Study of hard Multiple Parton Interactions in final states with photons and heavy flavors using the ALICE detector at the Large Hadron Collider

Supervisor(s): Paolo Bartalini (paolo.bartalini@cern.ch), Rachid Guernane (guernane@lpsc.in2p3.fr), Ingo Schienbein (schien@lpsc.in2p3.fr)

4. Measurement of the WWW production and Higgs boson property studies in pp collision recorded with the ATLAS detector at LHC

Supervisor(s): Emmanuel Monnier (monnier@cppm.in2p3.fr)

5. Upgrade of the ATLAS Calorimeter and of its trigger system with high end readout

Supervisor(s): Emmanuel Monnier (monnier@cppm.in2p3.fr)

6. Open heavy-flavour measurements via muons in proton-proton and Lead-Lead collisions with the ALICE detector at the CERN-LHC

Supervisor(s): Daicui Zhou (dczhou@mail.ccnu.edu.cn), Nicole Bastid (bastid@clermont.in2p3.fr), Philippe Crochet (crochet@clermont.in2p3.fr)

7. Discovering the Higgs boson produced in association with a top-antitop pair using boosting techniques with the ATLAS detector at the CERN LHC

Supervisor(s): Liang Li (l.li@cern.ch), Frédéric Déliot (frederic.deliot@cea.fr)

8. Prototype study for a Giant Radio Array for Neutrino Detection

Supervisor(s): Olivier Martineau (omartino@in2p3.fr), Wu XiangPing (wxp@bao.ac.cn)

PhD proposal n°1Optimization of a TPC detector for future e+/e- experiments: Study of distortions dues to space charge and ions feedbacks

Type of proposed PhD diploma: French□ Chinese □ French & Chinese X (tick correct answer)French host laboratory: CEA-SaclayChinese laboratory (if applicable): Tsinghua UniversityThesis advisor(s) and email(s): Roy Aleksan (roy.aleksan@cea.fr); Philippe Schwemling (Philippe.schwenling@cea.fr ) Planned date of start of stay in French lab: 2015, October 1Planned duration of stay in French lab (months): 36Expected date of thesis defense: 2018

Detailed description of the thesis subject: DESCRIPTION AND CONTEXT

Direct searches for signatures of physics beyond the Standard Model and the complementary approach of looking for deviations from Standard Model predictions in measurements of observables that can be computed with high precision will both be possible by 2030 at an e+e- collider, either a linear collider (ILC) or a circular (FCC-ee). In all cases, the detectors have to be of unequalled stability and precision, to allow measurement with a precision at the 10-5 level.An attractive detection technique for charge particles is the Time Projection Chamer (TPC). The principle is to bend the tracks corresponding to the charged particle trajectory in a magnetic field. The measurement of the curvature radius of the tracks gives a measurement of the particle momentum. When they cross the gaseous volume of the TPC, the particles leave an ionization trail of electron-ion pairs called primary ionization. The electrons from the primary ionization drift under the combined effect of the magnetic field and an electric field towards the end flanges of the detector. They are then amplified by avalanche effect by gaseous structures, like Charpak Multiwire Proportional Chambers in past detectors, and presently micro-etched detectors like Micromegas, whose spatial resolution is much better.The amplification mechanism generates a lot of of positive ions (secondary ionization), in addition to the primary ions coming from the primary ionization process. About 1% of the secondary ions end up in the detector drift volume, where they induce a space charge inducing distorsions on the electron trajectories, and as a consequence, distorsions on the track measurements. The target for FCC-ee and ILC is to limit this ion back flow phenomenon to less than 0.1%. To reach this goal, there is a significant amount of work to be

done, to get a detailed understanding of the phenomenon, and to design ion blocking systems, like gating grids.

Figure 1: Principle of operation of a TPC detector.

TEAM DESCRIPTION

The IRFU-SPP and IRFU-SEDI teams have solid experience in design and construction of gaseous detectors for physics experiments. They contributed in the past to the construction of the TPCs for the ALEPH and DELPHI detectors, as well as T2K recently. They are presently involved in the existing linear and circular e+/e- collider projects. There is also at IRFU a strong expertise on the Micromegas detectors (invented and developed by IRFU teams) and their applications.

PROPOSED WORK

We propose in this thesis to study experimentally the distorsions induced by positive ions on the charged tracks, and to study the amount of positive ions drifting back into the drift volume. This will be done using small to medium-scale detector prototypes. The measurements will be confronted to theoretical estimates from simulation. Building upon this study, the goal is to optimize the detector parameters, with the aim of minimizing the distorsions. The student will have to master progressively the whole workflow, starting from the design of prototypes, their realization, up to the final experimental data acquisision and analysis. Data acquisition will be done using cosmic muons, radioactive sources and test-beams (at CERN-Geneva, or DESY-Hamburg). Finally, the measurements of the distorsion will be used to predict the momentum resolution and invariant mass resolution of a complete detector system. The results on the resolutions will be used to check the expected detector performance for specific physics analyses, like the precision measurement of the Higgs boson mass in the HiggsStrahlung process.

Figure 2 : medium-scale(left) and small-scale TPC prototypes.

Candidates’ requested qualifications: Master-2 or equivalent academic level in instrumentation or elementary particle physics.

A basic knowledge of analog and digital electronics, of data acquisition systems and data processing techniques will be very useful.

ACQUIRED COMPETENCES

This thesis work will allow the sucessful candidate to acquire a lobal view of the design and detailed caracterization of a detection system. It will allow him also to develop his understanding of particle physics, and it will give him many occasions for partnership with industrial companies. The international aspects of the collaboration will give the candidate many academic opportunities abroad.

PhD proposal n°2

Beam halo and Compton process investigation using single crystal chemical vapour deposition diamond sensors at the ATF2 and PHIL electron beam lines

Type of proposed PhD diploma: French X Chinese □ French & Chinese □ (tick correct answer)French host laboratory: Laboratoire de l’Accelerateur Lineaire (LAL), CNRS-IN2P3Chinese laboratory (if applicable): Thesis advisor(s) and email(s): Philip Bambade, bambade@lal.in2p3.frPlanned date of start of stay in French lab: September or October, 2015Planned duration of stay in French lab (months): 36Expected date of thesis defense: September 2018

General description of the thesis subject: ATF2 is a 1.3 GeV electron accelerator facility operated at KEK (Japan), where an ultra low emittance beam can be focused to a transverse size of 40 nanometers. The main goal is validating the novel beam handling techniques needed for future high energy linear electron positron colliders. PHIL is a low energy photo-injector test accelerator operated at LAL for beam physics and instrumentation research. The thesis work at LAL will focus on developing the methodology for characterising and controling the beam halo distribution in both these beam lines, using a set of custom made radiation hard single crystal chemical vapour deposition diamond sensors prepared by the LAL group. In addition, at ATF2, the Compton recoil spectrum of the beam electrons interacting with the photons of the laser used to measure its size will be measured. The thesis project will involve modeling of the beam halo generation and propagation, usage and simulation of collimators needed for beam halo control, as well as preparation and testing of new diamond sensors. The selected student will have the opportunity to contribute to the operation of the accelerator facilities during the experimentation at LAL and KEK and to acquire hands-on beam physics skills.

Candidates’ requested qualifications: Applicants need to have a master's degree or equivalent in physics, have strong experimental and analytical skills, and be able to communicate at a scientific level in English. Prior experience in subatomic experimental physics and computing skills would be an advantage.

Detailed description of the thesis subject: The ILC (International Linear Collider) and CLIC (Compact Linear Collider) are two high energy electron positron colliders planned in the next decade [1,2] to complement the Large Hadron Collider (LHC) presently operating at CERN. Achieving the very high specified luminosities will require maintaining stably focused beams with nanometer transverse sizes at the collision point. For this purpose, ultra-low emittance beams must first be provided, through radiation damping of the particle phase space, in special storage rings similar to 3rd generation synchrotron light facilities. After acceleration, the beam sizes must be reduced by another factor of about 50 at the collision point. This is achieved via a new « final focus » concept, providing the needed optical demagnification through a sophisticated scheme with local control of the chromatic and geometric aberrations up to 3rd order [3].

The Accelerator Test Facility (ATF) is an international accelerator R&D complex based at KEK, operating an electron damping ring with transverse emittances reaching unprecedently low values of less than 2 nm and 10 pm in the horizontal and vertical planes, respectively [4]. In the past few years, ATF2, a low energy prototype of the final focus system for future linear colliders, has been added, using the extracted ultra-low emittance beam from ATF as input [5]. The main goals of both ATF and ATF2 are developing and validating the state of the art instrumentation and experimental beam handling techniques needed for

future linear colliders. The specific goals of the ATF2 project are to (1) produce and maintain over time a stable beam with transverse size smaller than 40 nanometers and (2) demonstrate 1-2 nanometer beam position stability at the collision point using bunch to bunch feedback. Two teams from IN2P3 laboratories participate in ATF2 within a community of American, Asian and European specialists.

A major issue in ATF2 and in linear colliders, as well as in many other accelerator facilities for high energy physics, is controling the beam halo before the collision point. Beam halo consists of tails extending far beyond the Gaussian core of the beam. Halo can be generated during the acceleration process, through wakefields and so-called « dark current » emission, as well as in the damping ring, via non-linearities, or through multiple Coulomb scattering of particles within bunches, scattering off the residual gas molecules in the vacuum chamber, and even scattering off photons from the black body thermal radiation present in the environment. From the experience at the Stanford Linear Collider (SLC) in the nineties and from more recent measurements at ATF, typically 10-3 of the total bunch charge can populate the halo. When tail particles reach the vacuum chamber and start showering in the material, large numbers of secondary particles are produced. The place where tail particles are the most likely to be intercepted are in the last focusing quadrupole magnets, just before the collision point. In a linear collider, such particle losses will be unacceptable near the collision point, as the produced secondary particles would have devastating effects on the experiments. For this reason, special collimation sections are planned far upstream in the system to clean up the beam halo. The design of these sections uses assumptions and experience from the SLC concerning the population and propagation of halo particles.

At ATF2, there are at present no collimators for the beam halo, although physical apertures of the vacuum chamber at various locations along the beam line will intercept some of it. Dedicated collimators are however now being prepared within the collaboration. The main tool to measure the beam size at the focal point of ATF2 is based on setting up an interference pattern between two laser beams and detecting the Compton scattered γ photon rate while the beam is scanned accross the interference fringes. From the modulation in the γ photon rate, the beam size could be extracted with a resolution as small as 20 nm [6]. This tool is however very sensitive to bremstrahlung photons emitted when halo particles are intercepted in the last quadrupole magnets and in the vacuum chamber after the collision point. Although specific collimation has been installed to shield the solid angle of the γ photon detector against such bremstrahlung photons, this background prevents the use of the largest horizontal and vertical demagnifications factors available in the optics. Recently, vertical beam sizes of 45 nm are routinely produced at low charge [7].

An alternative technique to measure the rate of Compton scatters during the interaction of the beam with the interference fringes is to detect the recoil electrons. Since these electrons have up to 2.23% lower energy compared to other beam particles, detection behind a large 20° bending magnet used after the collision point can be considered. The visibility in the presence of the beam halo was checked in simulation. While the halo is clearly dominating, by installing an extra focusing quadrupole between the collision point and the bending magnet, the halo can be focused enough to enable the edge and about half the Compton spectrum to be clearly measured. A new diamond sensors with four strips has been installed for this purpose in the vacuum chamber, near the beam, using a movable stage to scan the horizontal dimention [8]. A second one is planned in 2015 for scans in the vertical dimensions. The radiation that would have to be tolerated from backscattered neutrons and from the intercepted halo itself was estimated using a preliminary GEANT4 simulation, showing that the maximum yearly dose would be less than 25 kGy. This would be acceptable for scCVC diamonds. The electronics and signal processing chain are relatively simple given the large signal and low bunch frequency (1.5 to 6 Hz). However, the very large dynamic range implies special care to enable collecting the largest charges without biases at the higher end of the dynamic range. Shielding against high frequency electromagnetic pickup induced by the passage of the beam is also an issue in the lower end of the dynamic range.

In parallel, an identical device has been prepared to characterize the beam distribution at the exit of the PHIL facility at LAL, where the main aim is to provide a diagnostic capable of probing very low intensity beams suitable for detector R&D activities. PHIL is a facility at LAL for photo-cathode R&D with very short pulses [9]. Electron beams with 3-5 MeV, 10-500 pC, 7 ps FWHM bunches are produced daily, including for users doing other R&D. Recently, the high power sub-picosecond laser of the LASERIX team has been installed at LAL and it is planned to send a small fraction of its power onto the PHIL photo-cathode. A novel multi-photonic beam production mechanism is also being investigated at PHIL, to drastically reduce the beam charge, by reducing the photon energy on the photo-cathode below the threshold for extracting electrons, requiring hence coincident photons. The diamond sensor will be essential for tuning and operating in this multi-photon production mode.

Summarising, the main goals of the project to which the student will contribute are:

o Measure and characterise the beam halo for different optical magnifications and parameters at ATF2 and PHIL beam lines, respectively at KEK and LAL

o Simulate beam halo generation, propagation and experimental setupso Detect the recoil electron spectrum for linear (first order) Compton scatteringo Participate in R&D towards new diamond sensors with improved performanceso Contribute to the operation of the ATF2 and PHIL accelerators

Tentative timeline of the PhD preparation:The expected timeline is indicated below :

o Autumn 2015 : Basic accelerator concepts ; Participation in operation and experimentation with presently installed diamond sensor scanner at PHIL ; Study bibliography and do 241Sr β / 90Am source testing of first sensor fabricated at LAL.

o Winter – Summer 2016 : Simulation of the experimental setup at ATF2 with tracking and GEANT4 ; First experimentation period at ATF2 for beam halo studies. Beam testing after exit window of PHIL of LAL produced diamond sensor. General post-graduate course in accelerator physics and instrumentation (to be defined)

o Autumn 2016 – Summer 2017 : Add quadrupole focusing to experimental setup behind ATF2 collision point ; Halo and Compton spectrum measurements with collimation ; Contribute to ATF2 operation ; Further testing of LAL produced diamond sensors at PHIL ; Topical post-graduate training school during Summer (to be defined)

o Autumn 2017 – Summer 2018 : Analysis and interpretation of experimental data ; Detailed simulation and characterisation ; Extrapolation for future usage of diamond sensors for other facilities ; Documentation and public presentation (refereed publications, seminars) ; PhD writing and defense at Orsay.

Publications related to the PhD subject:1. R. Tomàs, Phys. Rev. STAccel. Beams 13, 014801 (2010), http://clic-study.org/ 2. ILC-REPORT-2007-001, http://www.linearcollider.org/cms/3. P. Raimondi and A. Seryi, Phys. Rev. Lett. 86, 37794. K. Kubo et al., Phys. Rev. Lett. 88, 194801 (2002), http://atf.kek.jp/collab/ap/5. P. Bambade et al., Phys. Rev. STAccel. Beams 13, 0142801 (2010)6. T. Suehara et al., Nucl.Instrum.Meth.A616:1-8 (2010)7. G. White et al, Physical Review Letters 112, 034802 (2014)8. S. Liu et al., http://accelconf.web.cern.ch/AccelConf/IPAC2014/papers/thpme091.pdf

See also:http://agenda.linearcollider.org/event/6389/session/14/contribution/51/material/slides/0.pdf

9. R. Roux et al., https://accelconf.web.cern.ch/AccelConf/LINAC2012

PhD proposal n°3

Study of hard Multiple Parton Interactions in final states with photons and heavy flavors using the ALICE detector at the Large Hadron Collider

Type of proposed PhD diploma: French□ Chinese x French & Chinese □ (tick correct answer)French host laboratory: LPSC - GrenobleChinese laboratory (if applicable): CCNU - WuhanThesis advisor(s) and email(s): - Prof. Paolo Bartalini paolo.bartalini@cern.ch, CCNU – Wuhan- Prof. Rachid Guernane guernane@lpsc.in2p3.fr, LPSC – Grenoble - Prof. Ingo Schienbein schien@lpsc.in2p3.fr, LPSC – Grenoble Planned date of start of stay in French lab: as soon as possiblePlanned duration of stay in French lab (months): 12Expected date of thesis defence: 2017-2018

Detailed description of the thesis subject:

In this study we focus on hard Multiple Parton Interactions (MPI), i.e. on processes with two or more separate hard scatterings in a single hadron-hadron or hadron-nucleus collision. The hard MPI may fake new physics or evidence of flow effects in dense matter, therefore its study is crucial to consolidate the knowledge of the corresponding relevant backgrounds. Investigating the hard MPI also provides a deep information on the hadronic structure of protons and nuclei. The study reported in this thesis constitutes a pilot project targeted on the data collected in the forthcoming RUN 2 that will deliver a much higher statistics compared to the former LHC runs. Further developments are foreseen at a later stage, the long term goal being to improve the knowledge of the initial state in hadron-hadron and hadron-nucleos interactions in particular for what concerns the MPI role.

The hard MPI properties in proton-proton and proton-nucleus collisions are studied measuring the extra jet production in direct photon events at different centre of mass energies and at different energy scales of the two hardest partonic interactions. Selecting extra jets with heavy flavor tagging significantly reduces the background from Single Parton Interactions. In order to keep an acceptable statistics for the rather rare events with two or more hard interactions in the same hadron-hadron or hadron-nucleus interaction it is essential to select photon and jets slightly above the perturbative pT threshold : this kinematic range turns out to be particularly well suited for the ALICE reach. Events with multiple quarkonia and multiple open charm or open beauty production are also investigated to further study the process- and energy scale- dependency of the MPI : here the unique ALICE particle identification features are also exploited.

The theoretical part of this research project mostly deals with the introduction of a new MPI model where the effective cross section is fully explicit. Accordingly, in a Monte Carlo implementation, the additional information can be represented by tuneable parameters achieving a direct indication on unknown properties of the hadron structure. The model is a natural basis for an extension to the case of proton-nucleus collisions, where the effects of MPI are sizably enhanced and which, due to the increased complexity of the target, allow access to even deeper properties of the non perturbative hadronic structure.

Candidates’ requested qualifications:

Young MSC with good curriculum studiorum, interested in an interdisciplinary PhD thesis in experimental/theoretical nuclear/particle physics.

Tentative timeline of the PhD preparation:

3-4 years. The main task of the PhD student in 2015 will be to optimize the experimental methodologies in

view of the RUN 2 data, in particular for what concerns the photon identification with the ALICE calorimeters (EMCal/DCal + PHOS), the heavy flavors identification with b-tagging algorithms and the exclusive reconstruction of b-hadron decays.

A significant amount of time will be invested in the development of the simulation tool mentioned in the TH part of the thesis description. Visiting the LPC – Grenoble laboratory will be essential to accomplish these two tasks that will be supervised by Prof. Guernane and Prof. Schienbein, respectively.

During the first twelve months the candidate will be based at CERN with regular visits to LPSC-Grenoble. Stationing at CERN will guarantee the continuous feedback of the relevant ALICE Physics Working Groups along with the supervision of Prof. Bartalini, who will advise on the MPI-related aspects of the thesis and will take care of editing the papers advertising the outcome of these studies.

In the future the candidate is expected to take a leading role in the continuous assessment of the ALICE physics reach for MPI processes both by the analysis of Run 2 data and detailed MC simulations in the context of the ALICE upgrade program which is also specifically dedicated to the high precision measurements of such rare probes at low pT.

Publications related to the PhD subject:

P. Bartalini et al. arXiv:1410.6664 and references therein ; F. Antinori et al. arXiv:1409.2981.

PhD proposal n°4

Measurement of the WWW production and Higgs boson property studies in pp collision recorded with the ATLAS detector at LHC.

Type of proposed PhD diploma: French□ Chinese □ French & Chinese X (tick correct answer)French host laboratory: CPPM (Center for Particle Physics Marseille)Chinese laboratory (if applicable): USTC – Department of Modern ScienceThesis advisor(s) and email(s): monnier@cppm.in2p3.frPlanned date of start of stay in French lab: 1/09/2015Planned duration of stay in French lab (months): 24 monthsExpected date of thesis defense: 09/2017

Detailed description of the thesis subject:The Large Hadron Collider (LHC) at CERN is today the only energy frontier machine in the world. ATLAS is one of the two general purpose experiments installed at the LHC that discovered in 2012 a Higgs boson, key piece for the understanding of the fundamental interactions and the origin of elementary particle mass. Its physics program extends beyond Higgs property measurements to the search for signs of physics beyond the Standard Model of particle physics.

In 2015, the LHC will restart its data taking at the new record 13 TeV center of mass energy. The record energy and high luminosity provided in the next three years will allow precise studies of the Higgs boson and its coupling properties in particular through multiboson final states or ttH final states. These key measurements, would allow confirming that the observed boson is the Standard Model Higgs boson, or could reveal New Physics.

The PhD thesis goal is to study the multiboson production in leptonic final states in the standard model and with an emphasis on the Higgs property studies. The new data taking conditions at the LHC (proton-proton collision center of mass energy increased to 13 TeV, high luminosity), which will resume data taking in spring 2015, will be particularly suited for this measurement. The sensitivity to the sub-dominant Higgs production modes will be increased, allowing for refined measurements of the Higgs couplings. During the thesis, detector performance studies will also be conducted especially linked to lepton identification with the ATLAS calorimeter system, key component of these multiboson studies.

Candidates’ requested qualifications: Particle physics

Tentative timeline of the PhD preparation: The candidate will contribute to the ATLAS data taking produced by the pp LHC accelerator in fall 2015 (13 TeV) and 2016(14 TeV) and will analyse those data to extract the Higgs properties in the WWW final state channel and search for new physics phenomena.Publications related to the PhD subject:Observation and measurement of Higgs boson decays to WW* with ATLAS at the LHC:https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CONFNOTES/ATLAS-CONF-2014-060/Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC: http://www.sciencedirect.com/science/article/pii/S037026931200857X

PhD proposal n°5

Upgrade of the ATLAS Calorimeter and of its trigger system with high end readout.

Type of proposed PhD diploma: French□ Chinese □ French & Chinese X (tick correct answer)French host laboratory: CPPM –Centre for Particle Physics MarseilleChinese laboratory (if applicable): IHEP,USTC,NANGING University, Shandong University…Thesis advisor(s) and email(s): E. Monnier – monnier@cppm.in2p3.frPlanned date of start of stay in French lab: Fall 2015Planned duration of stay in French lab (months): 36 monthsExpected date of thesis defense: fall 2018

Detailed description of the thesis subject:

The Large Hadron Collider (LHC) at CERN is today the only energy frontier machine in the world. ATLAS is one of the two general purpose experiments installed at the LHC that discovered in 2012 a Higgs boson, key piece for the understanding of the fundamental interactions and the origin of elementary particle mass. Its physics program extends beyond Higgs property measurements to the search for signs of physics beyond the Standard Model of particle physics.

In 2015, the LHC will restart its data taking at the new record 13 TeV center of mass energy. The record energy and high luminosity provided in the next three years will allow precise studies of the Higgs boson and its coupling properties in particular through multiboson final states or ttH final states. These key measurements, would allow confirming that the observed boson is the Standard Model Higgs boson, or could reveal New Physics. This scientific program will then be drastically increased by a major upgrade of the LHC that will be performed in the years to come combined to an equivalent upgrarde of the ATLAS detector and more particularly its calorimeter and trigger system.

CPPM and its ATLAS team is strongly involved in this scientific program. CPPM has contributed to the LAr Calorimeter design and construction as well as its operation and is now involved in its upgrade. CPPM has major responsibilities in all these parts as well as in the ATLAS pixel detector. CPPM also contribute heavily in every aspects of the data analysis with major responsibilities in it, being deeply involved in the recent Higgs discovery.

The PhD student will take part in the Upgrade program and is expected to make major contribution in the Liquid Argon (LAr) Calorimeter upgrade program. CPPM team is involved in the development of the caorlimeter trigger readout system. This system is based on high end data treatment electronic boards developed by scientists form sevral institutes including CPPM and based on the latest generation of FPGAs and optical links The thesis will be to contribute to theses electronic development that are above the industrial state of the art standards. A demonstrator will be connected to the ATLAS detector during the 2015 to 2017 data taking campaign allowing for the performance test of developed prototypes and the development and tuning of all the related imbedded firmware. This system readout ~40k channels over 10 Gb/s optical links has to reconstruct and treat the information in less than a few micro seconds for the subsequent trigger steps. The Phd thesis will be to have a major roles in all of theses phase from firmware development to performance assessment as well as demonstrator operation and data analysis leading to a system to be deployed in 2018. This thesis will allow the student to work in an international highly competitive and stimulating scientific environment working with world class engineers and physicists.

Candidates’ requested qualifications:

Experimental Physics, Electronics, FPGA, VHDL and advance software skills. Test system….

Tentative timeline of the PhD preparation

In fall 2015 the first prototypes will be available for firmware development and performances tests. These first prototypes will then be connected to a demonstrator on the LAr calorimeter front end electronic allowing advanced data taking and performance tests. In 2016 new prototypes will be developed and tested in the same ATLAS data taking demonstrator framework. Related FPGA firmware and surrounding software infrastructure will be developed and tested in parallel. In 2017, the final module will be produced and commissioned for an installation in 2018 and the global performances of the system will be assessed.

Publications related to the PhD subject:

ATLAS Liquid Argon Calorimeter Phase-I Upgrade Technical Design Report:http://cdsweb.cern.ch/record/1602230

ATLAS web site: http://atlas.ch/

PhD proposal n°6

Open heavy-flavour measurements via muons in proton-proton and Lead-Lead collisions with the ALICE detector at the CERN-LHC

Type of proposed PhD diploma: French□ Chinese □ French & Chinese X (tick correct answer)French host laboratory: Laboratoire de Physique Corpusculaire, CNRS/IN2P3, UMR6533, 24 Avenue des Landais, BP 80026, F-63171 AUBIERE Chinese laboratory (if applicable): Institute of Particle Physics (IOPP), Central China Normal University (CCNU), Key Laboratory of Quark & Lepton Physics, MoE, Luoyu Road 152, Wuhan 430079, ChinaThesis advisor(s) and email(s): Prof. Daicui Zhou (dczhou@mail.ccnu.edu.cn), Prof. Nicole Bastid (bastid@clermont.in2p3.fr), Dr Philippe Crochet (crochet@clermont.in2p3.fr) Planned date of start of stay in French lab: 01/11/2015Planned duration of stay in French lab (months): 36 (or 24), under discussionExpected date of thesis defense: November 2018

Detailed description of the thesis subject: The aim of ultra-relativistic heavy-ion collisions is to pin down the nuclear equation of state by studying the properties of nuclear matter under extreme conditions of temperature and pressure. The ultimate goal is to study the deconfinement of the hadron constituents in the so-called Quark-Gluon Plasma (QGP). This phase of matter is a prediction of Quantum ChromoDynamics (QCD) i.e. the theory of the strong interaction. It is believed that the Universe was made of a QGP a few microseconds after the Big Bang and that a QGP could be present in the core of neutron stars. The heavy-ion collision experimental program has started in the eighties at the Super Proton Synchrotron (SPS) at CERN and has then been pursued since 2000 at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven. With a nucleus-nucleus center-of-mass energy nearly 14 times larger than that reached at RHIC, the Large Hadron Collider (LHC) at CERN has been offering, since 2009, a totally new environment for systematic studies of the QGP. A Large Ion Collider Experiment (ALICE) is the unique LHC experiment dedicated to the study of heavy-ion collisions. The ALICE collaboration consists of 1550 physicists from 151 institutes in 37 countries. The detector is made of a central barrel, a small forward angle muon spectrometer and a set of detectors for event characterization and triggering. Amongst the various probes of the QGP, heavy quarks (charm and beauty) are of particular interest since, due to their large masses, they are mainly produced in hard scattering processes at the early stages of the heavy-ion collision and subsequently interact with the strongly-interacting medium formed in the collision. Open heavy-flavour particles are sensitive to the density of this medium through heavy quark in-medium energy loss mechanism. This effect is usually studied by means of the so-called nuclear modification factor: RAA(pT) = (dNAA/dpT) / (<TAA>.dpp /dpT) where <TAA> is the average nuclear overlap function corresponding to the considered collision centrality class; dNAA/dpT and dpp/dpT are the transverse momentum (pT) production yield and cross-section () in nucleus-nucleus (AA) and proton-proton (pp) collisions. According to QCD, quarks should lose less energy than gluons when passing through the medium. This is due to the colour-charge of gluons which is higher than that of quarks. In addition, heavy quarks are expected to lose less energy than light quarks due to the ``dead-cone'' effect. This colour-charge and mass-dependence of parton energy loss should therefore result in the following RAA hierarchy: R

AA < RDAA < RB

AA. First measurements have been performed and published (see below) with the data taken with the ALICE detector during the LHC Run1. In the LHC Run 2, the higher beam energy and luminosity will allow better precision measurements over a broader pT range. It will also make possible to build “double” ratios of RAA

(RAA(heavy flavours)/RAA(light flavours) and RAA(beauty)/RAA(charm)) which will allow to investigate in detail the features of in-medium parton energy loss. On the other hand, the study of heavy-flavour particle azimuthal anisotropy and the measurement of their elliptic flow can provide insight on the degree of thermalization of charm and beauty quarks in the medium and on the heavy-flavour hadronization

mechanism at low pT and intermediate pT, respectively. In the high pT region, the elliptic flow can constrain the path-length dependence of the in-medium parton energy loss. This is complementary to the study of parton energy loss. Here again, the larger statistics which will become available with the LHC Run 2 data will allow to extend the measurements done with the LHC Run 1 data at higher pT. Heavy flavours are measured in ALICE in the charm hadronic decay channels and in the semi-electronic decay channel at mid-rapidity and, in the semi-muonic decay channel at forward rapidity.The topic of the PhD thesis is the study of the heavy-flavour production in proton-proton (pp), and lead-lead (Pb-Pb) collisions via single muons measured with the ALICE muon spectrometer. A particular emphasis will be placed on the measurements in the high pT region.The manuscript will be organized in 6 chapters: 1) Introduction, 2) Heavy-flavour production as a probe of the QGP, 3) The ALICE experiment at the LHC, 4) Measuring heavy-flavours with the ALICE muon spectrometer, 5) Results and comparison to model predictions, 6) Conclusion. The first chapter consists of a general overview of heavy-ion collisions and QCD phase transitions. The second chapter presents the motivations for measuring heavy-flavours and their relevance for studying the QGP. In these two first chapters a comprehensive summary of the theoretical background and of the main experimental results obtained so far will be presented. Chapter three gives an overview of the ALICE experiment with a detailed description of the muon spectrometer. The ALICE data recording and analysis strategy are presented in chapter four. It includes the performance of the muon spectrometer for measuring the heavy-flavour production and the strategy followed at different steps of the analysis chain i.e. data reduction, background subtraction, acceptance x efficiency correction, normalization, estimation of systematic uncertainties etc. Finally, results are presented in chapter five. They are discussed and compared to other experimental measurements and to model predictions. A summary and the conclusions are given in the last chapter.The results obtained will be regularly presented in various meetings of the ALICE collaboration, as well as in international conferences and workshops, and then published.

Candidates’ requested qualifications: The candidate is already identified: Zuman Zhang from CCNU Wuhan. Zuman Zhang has already spent few months at LPC Clermont-Ferrand for his Master-I and Master-II trainings. He has all requested qualifications for the proposed PhD and has already started to get familiar, during his Master trainings, with the physics case and the ALICE data analysis tools.

Tentative timeline of the PhD preparation The PhD work will consist in participating to data taking with the ALICE detector at CERN. Then, the candidate will have to analyze the data, subtract the background and apply acceptance and efficiency corrections and normalization factors, and estimate the systematic uncertainties. The final results (production cross section, nuclear modification factor and elliptic flow) will be interpreted and compared to other experimental results and predictions from different models. Below is a rough estimate of the timeline.November 2015 - December 2015: participation in Pb-Pb data taking with the ALICE detector at CERN; first data analysis;January 2016 - summer 2017: Participation in proton-proton data taking with the ALICE detector at CERN; analysis of pp and Pb-Pb data; presentation of the results in meetings of the ALICE collaboration;Summer 2017: Presentation of the results in summer conferences;Summer 2017 - December 2017: finalization of the analyses and writing of the publication; December 2017: Participation in Pb-Pb data taking with the ALICE detector at CERN;January 2018 – October 2018: analysis of the 2017 Pb-Pb run and writing of the PhD manuscript. November 2018: PhD defense.

Publications related to the PhD subject: The 3 publications below are the result of the PhD of our former student from (Xiaoming Zhang) who has defended his PhD on May 2012. Two other publications on similar

topics are being prepared. One of them is the result of the work of our actual student (Shuang Li). Both PhD theses are co-tutorship Wuhan - Clermont-Ferrand.

B. Abelev et al. (The ALICE collaboration), Production of muons from heavy flavor decays at forward rapidity in pp and Pb-Pb collisions at sNN = 2.76 TeV, Phys. Rev. Lett. 109 (2012) 112301

B. Abelev et al. (The ALICE collaboration), Heavy flavour decay muon production at forward rapidity in proton-proton collisions at s = 7 TeV, Phys. Lett. B 708 (2012) 265

R. Averbeck, N. Bastid, Z. Conesa del Valle, P. Crochet, A. Dainese, X. Zhang, Reference heavy flavour cross sections in pp collisions at s = 2.76 TeV, using a pQCD-driven s-scaling of ALICE measurements at s = 7 TeV, arXiv:1107.3243 [hep-ph]

Conference proceedings related to the PhD subject: N. Bastid for the ALICE collaboration, Heavy-flavour and quarkonium measurements with ALICE

XI International Conference on hyperons, charm and beauty hadrons, Birmingham, UK, July 2014, Journal of Physics: Conference Series 556 (2014) 012020

S. Li for the ALICE collaboration, Heavy-flavour nuclear modification factor at forward and backward rapidity in p--Pb collisions at sNN = 5.02 TeV with ALICE at the LHC

XXIV international conference on ultra-relativistic nucleus-nucleus collisions (Quark Matter), Darmstadt, Germany, May 2014To be published in Nucl. Phys. A

S. Li for the ALICE collaboration, Nuclear modification factor and elliptic flow of muons from heavy-flavour decays in Pb--Pb collisions at sNN = 2.76 TeV with ALICE

6th International Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions (Hard Probes), Cape Town, South Africa, Nov. 2013To be published in Nucl. Phys. A

X. Zhang for the ALICE collaboration, Nuclear modification factor and elliptic flow of muons from heavy-flavour decays and muon elliptic flow in Pb--Pb collisions at sNN = 2.76 TeVStrangeness in Quark Matter 2013 (SQM), Birmingham, UK, July 2013Journal of Physics: Conference Series 509 (2014) 012045

X. Zhang for the ALICE collaboration, Nuclear modification factor of muons from open heavy-flavour decays and single muon elliptic flow at forward rapidity in Pb--Pb collisions at sNN = 2.76 TeV with ALICE

23th International conference on ultra-relativistic nucleus-nucleus collisions (Quark Matter), Washington, USA, August 2012Nucl. Phys. A 904 (2013) 977c

N. Bastid for the ALICE collaboration, Heavy-flavour and quarkonium measurements in Pb--Pb collisions at sNN = 2.76 TeV with ALICEHeavy Ion Collisions in the LHC Era, Quy Nhon, Vietnam, July 2012Journal of Physics: Conference Series 422 (2013) 012014

P. Crochet for the ALICE collaboration, Heavy flavour production measurements with ALICE at the CERN-LHC16th International Conference In Quantum Chromodynamics (QCD), Montpellier, France, July 2012Nucl. Phys. B 234 (2013) 325

P. Crochet, Heavy flavour production measurements at the CERN-LHCXLI International Symposium on Multiparticle Dynamics (ISMD), Miyajima Island, Hiroshima, Japan, Sept. 2011Progress of Theoretical Physics Supplement 193 (2012) 89

N. Bastid for the ALICE collaboration, Quarkonium and heavy flavour physics in pp and Pb--Pb collisions with the ALICE muon spectrometer at the LHC

International Workshop on Early Physics with Heavy-Ion Collisions at LHC, Bari, Italy, July 2011AIP Conf. Proc. 1422 (2012) 153

X. Lopez for the ALICE collaboration, Heavy flavour production in the semi-muonic channel in pp and Pb--Pb collisions measured with the ALICE experimentStrangeness in Quark Matter (SQM), Cracow, Poland, Sept. 2011Acta Phys. Polon. Supp. 5 (2012) 297

X. Zhang for the ALICE collaboration, Heavy flavour production cross section in the semi-muonic channel at forward rapidity in pp collisions at 7 TeV and measurement of its nuclear modification factor in Pb--Pb collisions at 2.76 TeV with ALICE22th International conference on ultra-relativistic nucleus-nucleus collisions (Quark Matter), Annecy, France, May 2011Journal of Physics G: Nuclear and Particle Physics 38 (2011) 124067

X. Zhang for the ALICE collaboration, Heavy flavour physics with the ALICE muon spectrometer at the LHCXLIX International Winter Meeting on Nuclear Physics, Bormio, Italy, Jan. 2011Pos (Bormio 2011) 030

N. Bastid for the ALICE collaboration, Quarkonium and heavy flavour physics with the ALICE muon spectrometer at the LHCInternational Conference on Hyperons, Charm and Beauty Hadron, Perugia, Italy, June 2010 Nucl. Phys. B (Proc. Suppl.) 210-211 (2011) 53

X. Zhang, L. Manceau, N. Bastid, P. Crochet, S. Grigoryan, D.C. Zhou for the ALICE collaboration, Measurement of (di)muons from heavy flavour decay in pp collisions at 14 TeV with ALICE at the LHC5th International conference on quarks and nuclear physics, Beijing, China, August 2009Chinese Physics C 34-9 (2010) 1538

ALICE Internal notes related to the PhD subject:

X. Zhang, N. Bastid, P. Crochet Measurement of the elliptic flow of muons from heavy-flavour decays at forward rapidity in Pb--Pb collisions at sNN = 2.76 TeVALICE-ANA-2013-921 (2013)

S. Li, X. Zhang, Z. Zhang, N. Bastid, P. Crochet Production of muons from heavy-flavour decays at forward rapidity in p--Pb and Pb--p collisions at = 5.02 TeV ALICE-ANA-2013-920 (2013)

L. Manceau, X. Zhang, N. Bastid, P. Crochet, S. Grigoryan and D. Zhou Performance of the ALICE muon spectrometer for the measurement of the B-hadron and D-hadron production cross sections in pp collisions at s = 14 TeV via single muonsALICE-INT-2011-xxx (2011)

L. Manceau, X. Zhang, N. Bastid, P. Crochet, S. Grigoryan and D. Zhou Performance of the ALICE muon spectrometer for the measurement of the B-hadron and D-hadron production cross sections in pp collisions at s = 14 TeVALICE-INT-2010-004 (2010)

PhD proposal n°7

Discovering the Higgs boson produced in association with a top-antitop pair using boosting techniques with the ATLAS detector at the CERN LHC

Type of PhD diploma: French□ Chinese □ French & Chinese (tick correct answer)French host laboratory: CEA at CERNChinese laboratory (if applicable): Shanghai Jiao Tong UniversityPlanned date of start of stay in French lab: summer 2015Planned duration of stay in French lab (months): 24Expected date of thesis defense: 2017Thesis advisor(s) and email(s): Liang Li (l.li@cern.ch), Frédéric Déliot (frederic.deliot@cea.fr)Description of the thesis subject :

The discovery of a new particle consistent with the Standard Model (SM) Higgs boson by the ATLAS and CMS experiments at the CERN’s Large Hadron Collider (LHC) in 2012 is a major milestone in our understanding of the subatomic world. One of the main goals in particle physics in the incoming years is now to understand the nature of this newly discovered particle and measure its properties. Studies of particular interest would be to understand the relation between the new particle and the heaviest elementary particle, the top quark. Indeed the Yukawa coupling of the top quark with the Higgs boson is expected to be of the order of one, much higher than for all the other fermions. The study of this coupling will give direct insight into the nature of the electroweak symmetry breaking mechanism and to potential physics beyond the SM. The only process which has a direct sensitivity to the top-quark Yukawa coupling is the production of a Higgs boson in association with a top-anti-top pair (ttH).

The ATLAS experiment is a multipurpose experiment that, along with the CMS experiment, has unprecedented capabilities to study the top quark and the Higgs boson. The LHC will resume operations in 2015 providing higher instantaneous luminosities and a higher center of mass energy of 13 TeV than in the previous Run.

Given the small expected ttH cross section, it is important to focus on the channel with the largest Higgs branching ratio. The more abundant Higgs decay channel is into a pair of b quarks. However ttH with H → bb is one of the most challenging channels at the LHC because of the large background from tt+jets. Discovering the ttH channel will require an excellent understanding of the SM background and of the detector performance. Some of these challenges can be overcome by using “boosted object” reconstruction techniques. The purity of the selected sample can be increased a lot by looking at relatively high transverse momentum top quarks and Higgs boson. Even if this requirement significantly reduces the signal yield, the decay products of the resonances are collimated into “fat” jets whose substructures can be studied in order to ease the mass reconstruction and improve its resolution. Boosting techniques have started to be applied successfully within the ATLAS collaboration in particular in searches for new resonances. Applying them to the ttH topology is relevant for the future LHC run at 13 TeV with high luminosity. With a ttH cross section around 4 times larger at 13 TeV, the goal of the PhD thesis is to achieve a first measurement of the ttH cross section using boosted techniques.

I have been contacted for a joint PhD project by a colleague in ATLAS, Prof. Liang Li from Shanghai Jiao Tong University (SJTU) in China. Both of us have already closely collaborated on single top quark physics at the D0 experiment. He has a PhD student who is just starting to work in ATLAS planning to focus on ttH measurement in the boosted final state. The CEA team based both at Saclay and at CERN is working on this topic since the beginning of 2014. If the SJTU student could join our team, he will be based at CERN with some visits to CEA-Saclay to collaborate on the software development, the background estimate and the

signal extraction. He will benefit from the strong CEA involvement at CERN both in hardware and analysis work. Being based at CERN will facilitate his research activities. The joint PhD program will also formalize the cooperation between SJTU and CEA.

Candidates requested qualifications:The candidate is expected to have a good knowledge of the basis of particle physics, andshould also be skilled with the C++ computer language. The working language at CERN is English or French.

Publications related to the PhD subject: 1. The ATLAS collaboration, Search for H→γγ produced in association with top quarks and constraints on the Yukawa coupling between the top quark and the Higgs boson using data taken at 7 TeV and 8 TeV with the ATLAS detector, arXiv:1409.31222. F. Déliot, N. Hadley, T. Schwarz, Properties of the Top Quark, submitted to Annual Review of Nuclear and Particle Science, to be published in November, 2014 (Volume 64)3. The ATLAS collaboration, Measurement of the charge asymmetry in top quark pair production in pp collisions at √s = 7 TeV using the ATLAS detector, JHEP 02, 107 (2014)4. The ATLAS, CDF, CMS and D0 collaborations, First combination of Tevatron and LHC measurements of the top quark mass, arXiv:1403.44275. The D0 collaboration, Observation of Single Top Quark Production, PRL103, 092001 (2009)

PhD proposal n°8

Prototype study for a Giant Radio Array for Neutrino Detection

Type of proposed PhD diploma: French x Chinese □ French & Chinese □ (tick correct answer) French host laboratory: LPNHE IN2P3-UPMC Paris Chinese laboratory (if applicable): NAOC Beijing Thesis advisor(s) and email(s): Olivier Martineau omartino@in2p3.fr, Wu XiangPing wxp@bao.ac.cn Planned date of start of stay in French lab: September 2015 Planned duration of stay in French lab (months): 3 years Expected date of thesis defense: September 2018

Detailed description of the thesis subject:

Cosmic neutrinos are very precious messengers of violent phenomena in the Universe. Neutral and interacting through weak interactions only, these particles propagate without interaction nor deflexion on cosmological distances. If their tiny cross sections make these particles so attractive for the study of the Universe, this property also makes their detection extremely complex. It requests in particular huge detection volumes together with a very strict rejection of background events. The experimental effort carried out since more than 20 years to detect cosmic neutrinos may reach a turning point, with the recent detection of 37 cosmic neutrino candidates by the IceCube collaboration [1]. However, only 2 of those have energies above 250TeV. Much larger detection volumes (typically effective volumes of several hundreds of km3) would be requested to reach a detection rate of neutrinos above 101(eV large enough to allow for the rise of neutrino astronomy. Radiodetection of extensive air showers (EAS) may constitute a valid solution to tackle this issue. Cosmic neutrinos could indeed induce air showers for Earth-grazing trajectories. Results obtained these last years by several experiments [2, 3, 4] show that EAS can be detected by radio antennas arrays. Cheap, easily transportable, with a stable response, radio antennas might be the valid technological choice foir a giant telescope. An international group of particle physicists, radioastronomers, astrohysicists, experimentalists and theoreticians presently think about a project of this type, called GRAND, for Giant Radio Array for Neutrino Detection. To validate this hypothesis, the priority is to prove that radio signals generated by EAS can be discriminated from background events with a high confidence level. The TREND collaboration is going to deploy a prototype array in summer 2015 on its experimental site (XinJiang, China) to investigate this issue and provide a quantitative estimation of the background rejection properties of the radio detection technique. The selected PhD candidate will participate in the deployment and validation of this setup. He will also be involved in the data analysis. This part of the work will request the presence of the PhD candidate for a significant period of time on the experimental site (typically 2 months/year), and will give a strong experimental bias to the PhD work. The estimation of the sensitivity of a giant radio array to cosmic neutrinos is another important aspect of the proposed PhD subject. This work, based on MC simulations, will be carried out in collaboration with researchers from the LPC Clermont-Ferrand laboratory, and the Institute of Astrophysics of Paris. This work shall lead to a detailed design proposition for a giant radio telescope dedicated to cosmic neutrino detection, and a precise estimation of the setup capacity to test the existing models for cosmic neutrino production. The relative weight of these 2 work axis will be discussed with the candidate.

Candidates’ requested qualifications:

Solid background in particle physics and astroparticles. Expertise in computing (Linux) and coding (C++, python) Publications related to the PhD subject: - D. Fargion, Astrophys.J.570 (2002) 909-925 arXiv :0002453 - D. Ardouin et al, the TREND collaboration, Astropart.Phys. 34 (2011) 717-731 arXiv:1007.4359