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

_Summary_:<br>
The search for new heavy particles is an important part of the physics program at the Large Hadron Collider (LHC) and has been the focus of an intense effort to uncover new physics beyond the Standard Model [1, 2, 3, 4] in a broad range of final states. In the cases where new heavy resonances would result from extensions of the SM gauge group, it is possible to systematically classify them and parameterize in terms of mass and couplings. Of particular interest are the singlet and the isospin triplet spin-1 resonances. For example, a generic model with isospin triplets formed by a new neutral Z boson (Z') and a pair of W bosons (W’), Heavy Vector Triplet (HVT) model, in case of flavour universality has four parameters, e.g. a mass and couplings to leptons (gl), quarks (gq) and Higgs and vector bosons (gH). Individual analyses only constrain a subset of these coupling parameters or have a limited sensitivity to them, but combination of channels leads to much stronger simultaneous constraints, exploiting their complementarity.

The ATLAS experiment has taken data for proton-proton collisions with &#8730;s = 13 !TeV since 2015 (Run 2) and collected a total amount of data of 149 fb-1 until the end of Run 2 in December 2018. The ATLAS Collaboration published the first result of a combination searches for new particles decaying to pairs of W or Z bosons (VV, where V represents either a W or Z boson), or to a W/Z boson with a Higgs boson (VH) and pairs for light leptons (ll/lv, where l=electrons or muons and v represents a neutrino) in 2018 by using a part of data taken in Run 2 that corresponds to an integrated luminosity of 36 fb-1 [5]. Our project aims the combination analysis with the full Run 2 dataset, where the VV/VH/ll/lv combination will be extended to other channels (di-jets, tt&#772;, tb&#772;, bb&#772;, &#964;&#964;, &#964;&#957;, etc.), placing even stronger constraints on different new physics scenarios. The addition of the 3rd generation final states is particularly interesting; it will bring much stronger constraints on a new heavy neutral gauge boson which couples preferentially to the second and third generation fermions [6]. Such constraints will have direct impact on the scenarios where the flavor anomalies observed in LHCb and B-factories in the semi-leptonic B-meson decays are explained by the new gauge boson. 

_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>
[1] Randall et al. Phys.Rev.Lett. 83 (1999) 3370-3373 hep-ph/9905221<br>
[2] Branco et al. Phys.Rept. 516 (2012) 1-102 arXiv:1106.0034 [hep-ph]<br>
[3] Contino et al. JHEP 1110 (2011) 081 arXiv:1109.1570 [hep-ph]<br>
[4] Pati et al. Phys.Rev. D10 (1974) 275-289, Erratum: Phys.Rev. D11 (1975) 703-703; Georgi et al. Phys.Rev.Lett. 32 (1974) 438-444; Fritzsch et al. Annals Phys. 93 (1975) 193-266<br>
[5] ATLAS Collaboration, Phys. Rev. D 98, 052008 (2018)<br>
[6] Faroughy et. al., Phys. Lett. B764 (2017) 126-134; Greljo & Marzocca Eur. Phys. J. C77 (2017) , 548; Di Luzio et al. JHEP 1811 (2018) 081<br>


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<center>HEP_14: *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]

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<center>HEP_15: *Test beams with the highly granular !SiW ECAL and implementation
of timing information* </center>

_Summary_:<br>

_French members_ :<br>
*R. Poeschl*, V. Boudry, F. Jimenez, J. Kunath, Y. Okugawa, D. Breton, J. Maalmi, J. Jeglot, S. Callier

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

_References_ :<br>


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

<center>HEP_16: *Flavour physics at Higgs Factories* </center>

_Summary_:<br>


_French members_ :<br>
*E. Kou*, R. Poeschl, F. Le Diberder, Y. Okugawa, F. Richard, D. Zerwas, P. Colas, M. Titov, M. Winter

_Japanese members_ : <br>
*D. Jeans*, K. Fujii, K. Yoshimasa, A. Ishikawa, T. Suehara, Y. Kiyo, Y. Hosotani, Y. Sumino, H. Yamamoto, S. Tomoyuki, J. Tian

_References_ :<br>


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Topic revision: r22 - 2022-11-28 - 01:42:11 - IsabelleRippBaudot
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