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<center>HEP_04: *Cosmological tests of Fundamental Physics* </center>

_Summary_:<br>
Several astrophysical or cosmological observations (evidences for dark matter, baryon asymmetry, inflation...) require an extension of the Standard Model of particle physics (so-called “beyond the standard model” (BSM) physics).  The links between cosmology and particle physics heavily rely on the understanding on the history of the universe, which is often based on standard assumptions. For instance: an inflationary epoch produces a quasi-power law spectrum of perturbations (seeds of current structures) and ends in a radiation dominated period, during which  conventional  electroweak symmetry and QCD breaking happen as crossovers, according to the SM.  Dark Matter is usually considered to be a particle relic, once in thermal contact with other SM species, etc. We are exploring possible departures from this simple picture. In the classically conformal extension of the SM, S. Iso, P. Serpico, and K. Shimada found that the chiral condensation in QCD can play an important role in the dynamics of the electroweak symmetry breaking. The phase transition becomes of the first order type and accordingly generates large gravitational waves that can be detected by future gravitational wave detectors [2]. Further consequences of this scenario, such as signatures of a late thermal inflationary phase and implications for dark matter, are being investigated. Always related to gravitational waves, it is well known that the LIGO interferometers have detected their first sources of gravitational waves, from coalescences of binary black holes (BHs). While such binaries have long been considered an attractive candidate, the mechanism to produce them is not established, yet, in particular for such high masses (about 30 times the mass of the sun). It has also been conjectured that such BH may be of primordial origin. Their formation requires a significant departure from the simplest inflationary models, and at the same time it would lead to non-standard cosmological signatures, which can be searched for. In [3], we studied the impact of accretion of primordial stellar mass black holes on  CMB anisotropies, finding stringent bounds. We are currently extending this study to massive and supermassive primordial black holes, which requires a careful treatment of the accretion in presence of a “dark matter” halo surrounding the black hole. 

_French members_:<br>
*V. Poulin*, 
P. Serpico,
J. Lavalle,
G. Facchinetti, 
G. Franco Abellan, 
R. Murgia


_Japanese members_: <br>
*N. Hiroshima*,
K. Kohri,
S. Iso,
T. Sekiguchi,
H. Matsui,
T. Igata

_References_:<br>
[1] S. Iso, K. Kohri and K. Shimada,
"Dynamical fine-tuning of initial conditions for small field inflation,"
  Phys. Rev. D  93, 084009 (2016)
  [arXiv:1511.05923]<br>
[2] S. Iso, P. D. Serpico and K. Shimada, "QCD-Electroweak first order phase transition in supercooled universe,''  
 Phys. Rev. Lett. 119, 141301 (2017)  [arXiv:1704.04955] <br>
[3]  V. Poulin, P. D. Serpico, F. Calore, S. Clesse and K. Kohri,
“CMB bounds on disk-accreting massive primordial black holes,''
  Phys. Rev. D  96,  083524 (2017)
  [arXiv:1707.04206]

<center>------------------------------ </center>


<center>HEP_07: *SiW ECAL* </center>

_Summary_:<br>
A compact and highly granular electromagnetic calorimeter is one of the key requirements for PFA high precision jet reconstruction, and for full realization of ILC's physics potential.
The aim of this project is R&D of a silicon-tungsten calorimeter.
The main aim is to further develop the "technical prototype", in which different technical approaches to detector construction are tested and compared.
Aspects to be investigated include improvements in electrical design, thinner front-end boards, and silicon sensors of varying thickness.
Several beam tests of this prototype are foreseen during the year.
An important milestone is to develop a "long slab", chaining several unitary elements to make a large detector element, as will be needed in a full detector.
Physics analyses which make significant use of the ECAL will be further studied, with an emphasis on the reconstruction and use of tau lepton decays to probe for new physics.
An important aspect will be to quantify how different ECAL design choices (which may, for example, involve significantly different costs) impact such analyses.

_French members_:<br>
*V. Boudry*, F. Jimnez, J. Kunath, R. Poeschl, A. Irles

_Japanese members_: <br>
*D. Jeans*, T. Suehara, K.Kawagoe, T. Yoshioka

_References_:<br>
[1] T.H.Tran, "ILD !SiW ECAL and sDHCAL dimension-performance optimisation", report at LCWS'13, arXiv:1404.3173 [physics.ins-det]<br>
[2] Ch.Kozakai et al., "Robustness of a !SiECAL used in Particle Flow Reconstruction", report at LCWS'13, arXiv:1404.0124 [physics.ins-det]<br>
[3] T.Tomita et al., "A study of silicon sensor for ILD ECAL", report at LCWS'13, arXiv:1403.7953 [physics.ins-det]<br>
[4] Editors: T.Behnke et al., "The International Linear Collider Technical Design Report - Volume 4: Detectors", arXiv:1306.6329 [physics.ins-det]

_website_:<br>
 https://twiki.cern.ch/twiki/bin/view/CALICE/SiWEcal

<center>------------------------------ </center>


<center>HEP_09: *ILC Heavy Flavours* </center>

_Summary_:<br>
The ILC Physics Case can be summarized in two main domains:
precision measurements and discovery potential.
Whereas the principal aim of the precision measurements concerns the Higgs, 
a secondary but very important aim is to study the top: to determine accurately its mass
and to measure its couplings to the SM vector bosons.
The top mass will be obtained at 350 !GeV, by scanning the threshold of the top pair production.
The top couplings to the photon and the Z0 will be measured at about 500 !GeV.
<br>
For both measurements, a precise mastering of the !ElectroWeak loop corrections is essential since
it appears that they induce sizeable corrections to the leading mechanisms (typically 5-10%)
far larger than the precision achievable at the ILC.
<br>
The goals of the !TYL project “top-ILC” are twofold: strengthen further the 500 !GeV analysis that has been developed in the past years using semi-leptonic events [1], and design means to control theoretically and experimentally the !ElectroWeak loop corrections.
<br>
In that respect, following the first top-ILC workshop held in !KeK (2013) one of the approach that is pursued is to assess the potential of the 
double leptonic events, where both W’s decay leptonically.
<br>
Using Monte Carlo events provided by GRACE [2], it has been shown that experimentally one can cope with the two missing neutrinos and that a Matrix Element [3] analysis of the events 
using Leading Order expressions [4] should provide top-coupling measurements with an accuracy similar to the one attained using the semi-leptonic events, but with different systematical effects.

_French members_ :<br>
*R. Poeschl*, A. Irles, E. Kou, F. Le Diberder, F. Richard, P. Colas, M. Titov, M. Winter

_Japanese members_ : <br>
*K. Fujii*, Y. Hosotani, D. Jeans, Y. Kiyo, M. Kurata, Y. Kurihara, T. Suehara, Y. Sumino, T. Tanabe, J. Tian, H Yamamoto, A. Ishikawa

_References_ :<br>
[1] M.S. Amjad et al. : arXiv:1307.8102 (2013) <br>
[2] Progress of Theoretical Physics, Vol. XX, No. X, October 1999 <br>
[3] H.J. Behrends et al., CELLO Collab. Z. Phys. C43 (1989)  <br>
[4] G. Kane, G. Ladinsky and C.P. Yuan, Phys. Rev. D 45 (1992) <br>

<center>------------------------------ </center>


<center>HEP_10: *Strong dynamics beyond the Standard Model at LHC and Future Colliders* </center>

_Summary_:<br>
This project considers models that arise from a new strong interaction that can be defined in terms of a simple, confining, gauge group and a number of fundamental fermions which form bound states allowing a more fundamental explanation of weak interactions and of the Higgs sector of the Standard Model (SM). In particular we use effective field theory description of the models based on the properties of the higher-energy completion in terms of the fundamental fermions, including the masses and couplings of the light pseudo-Goldstone bosons (pNGB). Vector and fermionic composite states are also typically present. We study the implications for the LHC at its High Luminosity and High Energy extensions as well as at the ILC. Apart from the focus on discovering new particles associated to this new strong sector, small deviations in the properties of SM particles is also expected. These models, named in general “Composite Higgs models”, are analogous to QCD, and typically require numerical tools to compute masses and couplings of the bound states. Non-minimal realizations of this idea are partially discussed in the recent literature but their phenomenology at present and future colliders is not fully studied. In particular these models contain extra particle bound states, both bosons of spin 0 and 1 and fermions. These particles may be or not protected by symmetries which implies very different phenomenological expectations. The lattice simulations are quite time consuming and expensive, therefore it will not be possible to fully explore in this way all these models. Alternative methods, based on the previous collaborations of the French and Japanese group are used to explore this subject. 

_French members_:<br>
* A. Deandrea*, G. Cacciapaglia, C. Cot, S. Vatani

_Japanese members_: <br>
*M. Hashimoto*, Y. Okada, D. Harada




<center>------------------------------ </center>


<center>HEP_11: *Looking for dark-sector long-lived particles with ATLAS* </center>

_Summary_:<br>

_French members_:<br>
*M.-H. Genest*, N. Lalloue, D. Portillo Quintero

_Japanese members_: <br>

_References_:<br>
*K. Hara*, S. Wada, K. Nakamura, F. Ukegawa

<center>------------------------------ </center>


<center>HEP_12: *Stronger together to search for new heavy resonances in ATLAS* </center>

_Summary_:<br>

_French members_:<br>
*T. Berger Hryn’ova*, S. Calvet, R. Camacho Toro, J. Donini

_Japanese members_: <br>
*Y. Takubo*, K. Terashi, K. Nagano

_References_:<br>


<center>------------------------------ </center>


<center>HEP_13: *Higgs physics at the ILC* </center>

_Summary_:<br>

_French members_:<br>
*J.-C. Brient*, J. Knuth

_Japanese members_: <br>
*J. Tian*, D. Jeans

_References_ :<br>
Topic revision: r19 - 2020-09-17 - 11:21:48 - IsabelleRippBaudot
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