Integration of the fcc-ee detector in the fcc-ee Final Focus



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Integration of the FCC-ee detector in the FCC-ee Final Focus

Emmanuel Perez


The FCC-ee study is part and parcel of the Future Circular Collider design study undertaken at CERN since the beginning of 2014. It is exploring the potential of a high-luminosity e+e- circular collider, performing an in-depth analysis of infrastructure and operation concepts and considering the technology research and development programs that would be required to build a future circular collider. A conceptual design report will be delivered before the end of 2018, in time for the next update of the European Strategy for Particle Physics.
In the interaction region foreseen for the FCC-ee, several machine elements need to get very close to the interaction point, which leaves little space for the forward instrumentation. The best way to insert the forward detectors, such that they achieve their goals without inducing large backgrounds in the main detector, remains to be determined. The goal of this project is to perform simulations pertaining to these issues.
The first step consists in implementing a possible design of the FCC-ee forward region in a full simulation framework (starting from existing tools): the main machine elements, the magnetic configuration, and an example luminosity monitor. The effect of machine-induced background (synchrotron radiation) and of beam-induced background sources (pair-production, hadron production from gamma-gamma interactions, radiative Bhabha scattering) in the main detector will then be evaluated, for the conditions corresponding to each center-of-mass energy of the machine. Consequences for the vertex detector, in which the beam-induced background is expected to be largest, will be assessed. These background studies will also have consequences for the trigger system of the experiment, which will be studied as well.
The fellow will also use these simulations in order to study how the luminosity could be measured at the FCC-ee. The precision expected from the measurement of low-angle Bhabha scattering, using a forward luminometer, will be evaluated for different configurations of this luminometer (corresponding to a different acceptance, granularity, resolution), in presence of the backgrounds. The alternative possibility of measuring the luminosity from large angle di-photon production will be considered as well.
A last aspect of the project, if time allows, consists in simulating a low-angle "beam-calorimeter", traditionally useful for beam monitoring and for tagging the forward electrons in gamma-gamma processes. At the FCC-ee, this detector would have to be installed behind the focusing quadrupole. Simulations need to be done to determine whether or not this would prevent such a detector to deliver useful data.
FCC-ee detector full simulation

Andrea Dell’Acqua


Future Circular Collider (FCC) is an integral conceptual design study for post LHC particle accelerator options in a global context. The Future Circular Collider study has an emphasis on proton-proton and electron-positron (lepton) high-energy frontier machines. It is exploring the potential of hadron and lepton circular colliders, performing an in-depth analysis of infrastructure and operation concepts and considering the technology research and development programs that would be required to build a future circular collider. A conceptual design report will be delivered before the end of 2018, in time for the next update of the European Strategy for Particle Physics.
In view of the design report, simulation and reconstruction software is being developed in order to study the physics potential of the FCC options and to establish the experimental requirements to be met. The software shall be common to all FCC options and sufficiently generic to accommodate the complete range of simulation studies required at the design stage. Wherever possible, it should profit and reuse existing packages and options developed both by the LHC experiments and other ongoing design project, such as those for the ILC and CLIC.
The fellow candidate will participate in the development and the deployment of the FCC simulation software, with a particular emphasis to the FCC-ee case. He/she will collaborate in the development of a detector simulation suite in which he/she will take care to implement the electron-positron scenario, from physics requirements to physics generators to the implementation of detector geometries and read-out schemes. As many simulation tools were already developed for the CLIC scenario, he/she will also ensure that the CLIC simulation and detector geometries can be exported and used in the FCC simulation software and can be utilized as a starting point for the FCC studies.
Additionally, the candidate will act as contact person to working groups involved in machine background studies and detector development in order to collect information and requirements and make sure that these are promptly implemented in the simulation software.
Possible involvement in tracking studies as well as reconstruction software can be considered.

Generic particle-flow reconstruction at the FCC

Patrick Janot (CERN), Colin Bernet (IPN Lyon et Université Claude Bernard)


The design study of the Future Circular Colliders (FCC) was initiated at CERN at the beginning of 2014, to identify post-LHC accelerator projects at the high-energy frontier. The study has an emphasis on proton-proton (FCC-hh) and electron-positron (FCC-ee) colliders, and includes the design and optimization of the pertaining detectors that would comply with the physics programme of both machines. A conceptual design report will be delivered before the end of 2018, in time for the next update of the European Strategy for Particle Physics.
With the successful experiences of the ALEPH detector at LEP and of the CMS detector at LHC, there is now a general consensus that particle-flow reconstruction is the optimal way to analyse collisions final states, be it at with e+e- or pp colliders. With up to four detectors at the FCC-ee, on the one hand, and at the FCC-hh, on the other, the development of up to eight, detector-specific, particle-flow reconstruction algorithms would have to be envisioned.
The selected doctoral student will instead develop a generic, detector-independent, algorithm, starting from a list of charged particle tracks and vertices, calorimeter clusters, and muon tracks, to deliver a list of identified particles for later use in any physics analysis. Previous experience from ALEPH, CMS, and Linear Collider studies will be used throughout. Initially, the developments will focus on the simpler final states from e+e- collisions. The compliance of the algorithm with more involved final states from pp collisions will be checked with CMS, with bot the current detector and real data, and the projected detector upgrade for the high-luminosity LHC.
Additionally, if time allows, the candidate will develop calorimeter-clustering algorithms that will optimally benefit from the available detector space-time granularity, and will participate in the optimization of generic tracking algorithms for use in the particle flow reconstruction.
Beam Energy Calibration at the FCC-ee

Jorg Wenninger (CERN), Alain Blondel (Université de Genève)


The FCC-ee study is part and parcel of the Future Circular Collider design study undertaken at CERN since the beginning of 2014. It is exploring the potential of a high-luminosity e+e- circular collider, performing an in-depth analysis of infrastructure and operation concepts and considering the technology research and development programs that would be required to build a future circular collider. A conceptual design report will be delivered before the end of 2018, in time for the next update of the European Strategy for Particle Physics.
Beam-energy measurement using the resonant spin depolarization method in a systematic way is an essential ingredient to the FCC-ee physics program, potentially allowing achievement of precisions of better than 100keV on the Z boson mass (1ppm) and on the Z boson width; and 500 keV on the W mass, precision that were unheard of until recently. The work will be performed within a dedicated polarization group of the FCC-ee study and in connection with the physics studies.
The selected student will benefit and learn from the experience of the world experts on the topic, who accumulated theoretical knowledge and experimental know-how with the LEP collider in the nineties. She/he will apply this experience to the master and simulate the FCC-ee configuration to predict the level of polarization expected at the various centre-of-mass energies, and will participate in the simulation of the spin-depolarization experiment. The student will also investigate the consequences of the findings on the physics performance, which will be the proposed subject of his/her PhD thesis.

High-granularity calorimetry at the FCC-ee

Luca Malgeri (CERN)


To be written.

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