Concept# Strange quark

Summary

The strange quark or s quark (from its symbol, s) is the third lightest of all quarks, a type of elementary particle. Strange quarks are found in subatomic particles called hadrons. Examples of hadrons containing strange quarks include kaons (Kaon), strange D mesons (Strange D), Sigma baryons (Sigma), and other strange particles.
According to the IUPAP, the symbol s is the official name, while "strange" is to be considered only as a mnemonic. The name sideways has also been used because the s quark has an I3 value of 0 while the u ("up") and d ("down") quarks have values of +1/2 and −1/2 respectively.
Along with the charm quark, it is part of the second generation of matter. It has an electric charge of −1/3 e and a bare mass of 95MeV/c2. Like all quarks, the strange quark is an elementary fermion with spin 1/2, and experiences all four fundamental interactions:

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This thesis presents a general discussion of the Composite Higgs scenario of Electro-Weak Symmetry Breaking (EWSB). We start by reviewing the Standard Model of Electro-Weak interaction, discussing its experimental tests and conceptual pitfalls. Emphasis is given to the effective field theory point of view. In particular, the inherent tension related to the stability of the Electro-Weak scale motivates us to explore the possibility of having the Higgs field emerging as a Nambu-Goldstone boson from a new strongly coupled sector. Our construction is to a large extent inspired by the picture of the long range dynamics of QCD. The main ingredients are the symmetry of the UV theory, the pattern of its spontaneous breakdown and the sources of explicit breaking. In QCD, the latter are provided by the light quark masses and by the electromagnetic interaction. In Composite Higgs models, the most relevant symmetry breaking couplings are those related to the generation of the third family quark Yukawas through partial compositeness. They generate a potential for the Higgs and thus trigger EWSB. The constraints on the scenario are exposed, with a particular emphasis on the composite Two Higgs Doublet Model (THDM). While a residual SO(4) symmetry is sufficient to ensure a realistic phenomenology in presence of a single composite Higgs doublet, an extended Higgs sector needs more symmetries. For two doublets we show how either CP or a ℤ2 symmetry can play this role and construct a model for each realisation relying on the SO(6)/SO(4) × SO(2) coset. Finally, we discuss the phenomenology of this scenario. In particular, we present de differences between an elementary and a composite THDM. We also conclude that composite fermions associated to the third family quarks seem to be the most promising experimental handles for these models. We discuss their discovery range at the LHC, and the possibility of measuring the structure of their couplings. This knowledge would allow important insight into the strong dynamics.

Muhammad Ahmad, Georgios Anagnostou, Guido Andreassi, Konstantin Androsov, Tagir Aushev, Thomas Berger, Michele Bianco, Rakesh Chawla, Chunhui Chen, Yixing Chen, Tian Cheng, Pratyush Das, João Miguel das Neves Duarte, Abhisek Datta, Milos Dordevic, Dipanwita Dutta, Matthias Finger, Francesco Fiori, Sebastiana Gianì, Ruchi Gupta, Seungkyu Ha, Csaba Hajdu, Peter Hansen, Miao Hu, Muhammad Ansar Iqbal, Alexis Kalogeropoulos, Viktor Khristenko, Donghyun Kim, Doohyun Kim, Ji Hyun Kim, Ajay Kumar, Mithlesh Kumar, Vineet Kumar, Sanjeev Kumar, Ekaterina Kuznetsova, Federica Legger, Yiming Li, Jing Li, Zhen Liu, Werner Lustermann, Maren Tabea Meinhard, Ioannis Papadopoulos, Anton Petrov, Vladimir Petrov, Marco Pisano, Jessica Prisciandaro, Andrea Rizzi, Paolo Ronchese, Valérie Scheurer, Sourav Sen, Arvind Shah, Varun Sharma, Ashish Sharma, Wei Shi, Kun Shi, Muhammad Shoaib, Bandeep Singh, Jan Steggemann, Wei Sun, Andromachi Tsirou, David Vannerom, Joao Varela, Yi Wang, Jian Wang, Xiao Wang, Hui Wang, Zheng Wang, Qian Wang, Siyuan Wang, Muhammad Waqas, Matthias Weber, Matthias Wolf, Meng Xiao, Yong Yang, Kai Yi, Hua Zhang, Yi Zhang, Jian Zhao

The Xi(-)(b)pi(+)pi(-) invariant mass spectrum is investigated with an event sample of proton-proton collisions at root s = 13 TeV, collected by the CMS experiment at the LHC in 2016-2018 and corresponding to an integrated luminosity of 140 fb(-1). The ground state Xi(-)(b) is reconstructed via its decays to J/psi Xi(-) and J/psi Lambda K-. A narrow resonance, labeled Xi(b)(6100)(-), is observed at a Xi(-)(b)pi(+)pi(-) invariant mass of 6100.3 +/- 0.2(stat) +/- 0.1(syst) +/- 0.6(Xi(-)(b)) MeV, where the last uncertainty reflects the precision of the Xi(-)(b) baryon mass. The upper limit on the Xi(b)(6100)(-) natural width is determined to be 1.9 MeV at 95% confidence level. The low Xi(b)(6100)(-) signal yield observed in data does not allow a measurement of the quantum numbers of the new state. However, following analogies with the established excited Xi(c) baryon states, the new Xi(b)(6100)(-) resonance and its decay sequence are consistent with the orbitally excited Xi(- )(b)baryon, with spin and parity quantum numbers J(P) = 3/2(-).

2021Muhammad Ahmad, Georgios Anagnostou, Konstantin Androsov, Alexandre Aubin, Roberto Castello, Juan Ramon Castiñeiras De Saa, Yixing Chen, Tian Cheng, Davide Cieri, Giuseppe Codispoti, Alessandro Degano, Charles Dietz, Milos Dordevic, Dipanwita Dutta, Matthias Finger, Francesco Fiori, Daniel Gonzalez, Ruchi Gupta, Csaba Hajdu, Peter Hansen, Alexis Kalogeropoulos, Viktor Khristenko, Ji Hyun Kim, Donghyun Kim, Vineet Kumar, Ajay Kumar, Sanjeev Kumar, Ekaterina Kuznetsova, Wei Li, Ho Ling Li, Shuai Liu, Hao Liu, Werner Lustermann, Bibhuprasad Mahakud, Matteo Marone, Thomas Muller, Ioannis Papadopoulos, Vladimir Petrov, Quentin Python, Andrea Rizzi, Paolo Ronchese, Sourav Sen, Varun Sharma, Ashish Sharma, Lesya Shchutska, Muhammad Shoaib, Michal Simon, Gurpreet Singh, Jan Steggemann, Xin Sun, Wei Sun, Marco Trovato, Andromachi Tsirou, Paul Turner, Joao Varela, Rui Wang, Qian Wang, Yi Wang, Siyuan Wang, Zheng Wang, Jian Wang, Matthias Weber, Matthias Wolf, Fan Xia, Meng Xiao, Zhirui Xu, Fan Yang, Yong Yang, Kai Yi

A search for a light charged Higgs boson, originating from the decay of a top quark and subsequently decaying into a charm quark and a strange antiquark, is presented. The data used in the analysis correspond to an integrated luminosity of 19.7 fb$^{−1}$ recorded in proton-proton collisions at $\sqrt{s}=8$ TeV by the CMS experiment at the LHC. The search is performed in the process $\mathrm{t}\overline{\mathrm{t}}\to {\mathrm{W}}^{\pm }{\mathrm{b}\mathrm{H}}^{\mp}\overline{\mathrm{b}}$ , where the W boson decays to a lepton (electron or muon) and a neutrino. The decays lead to a final state comprising an isolated lepton, at least four jets and large missing transverse energy. No significant deviation is observed in the data with respect to the standard model predictions, and model-independent upper limits are set on the branching fraction $\mathrm{\mathcal{B}}\left(\mathrm{t}\to {\mathrm{H}}^{+}\mathrm{b}\right)$ , ranging from 1.2 to 6.5% for a charged Higgs boson with mass between 90 and 160 GeV, under the assumption that $\mathrm{\mathcal{B}}\left({\mathrm{H}}^{+}\to \mathrm{c}\mathrm{s}\right)=100\%$ .

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