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2022 ◽  
pp. 115672
Author(s):  
Jin-Zhong Han ◽  
Jing Yang ◽  
Shuai Xu ◽  
Han-Kui Wang
Keyword(s):  

2021 ◽  
Vol 2021 (12) ◽  
Author(s):  
◽  
G. Aad ◽  
B. Abbott ◽  
D. C. Abbott ◽  
A. Abed Abud ◽  
...  

Abstract The fragmentation properties of jets containing b-hadrons are studied using charged B mesons in 139 fb−1 of pp collisions at $$ \sqrt{s} $$ s = 13 TeV, recorded with the ATLAS detector at the LHC during the period from 2015 to 2018. The B mesons are reconstructed using the decay of B± into J/ψK±, with the J/ψ decaying into a pair of muons. Jets are reconstructed using the anti-kt algorithm with radius parameter R = 0.4. The measurement determines the longitudinal and transverse momentum profiles of the reconstructed B hadrons with respect to the axes of the jets to which they are geometrically associated. These distributions are measured in intervals of the jet transverse momentum, ranging from 50 GeV to above 100 GeV. The results are corrected for detector effects and compared with several Monte Carlo predictions using different parton shower and hadronisation models. The results for the longitudinal and transverse profiles provide useful inputs to improve the description of heavy-flavour fragmentation in jets.


2021 ◽  
Vol 104 (3) ◽  
Author(s):  
Debajyoti Choudhury ◽  
Kuldeep Deka ◽  
Nilanjana Kumar
Keyword(s):  

2021 ◽  
Vol 81 (5) ◽  
Author(s):  
Lin Han ◽  
Jie-Fen Shen

AbstractNew vector-like quarks are predicted in many new physics scenarios beyond the Standard Model (SM). Based on a model-independent framework, we investigate the prospect of discovering the SU(2) singlet vector-like bottom quark (VLQ-B) in $$e^{+}e^{-}$$ e + e - collisions at 3 TeV Compact Linear Collider. We study the single VLQ-B production process $$e^{-}e^{+}\rightarrow B{\bar{b}}\rightarrow Zb{\bar{b}}$$ e - e + → B b ¯ → Z b b ¯ with two types of decay channel: $$Z\rightarrow \ell ^{+}\ell ^{-}$$ Z → ℓ + ℓ - , and $$Z\rightarrow \nu {\bar{\nu }}$$ Z → ν ν ¯ . By carrying out a full simulation for the signals and the relevant SM backgrounds, the $$2\sigma $$ 2 σ exclusion limit and $$5\sigma $$ 5 σ discovery prospects are, respectively, obtained on the B quark mass and the coupling strength $$g^{*}$$ g ∗ with the integrated luminosity of 5 $$\hbox {ab}^{-1}$$ ab - 1 . Our numerical results show that the possible signals of the singlet VLQ-B might be detected at the future high-energy $$e^{+}e^{-}$$ e + e - linear colliders.


2021 ◽  
Vol 81 (4) ◽  
Author(s):  
Bo-Cheng Yang ◽  
Liang Tang ◽  
Cong-Feng Qiao

AbstractVery recently, the LHCb Collaboration observed distinct structures with the $$cc{\bar{c}}{\bar{c}}$$ c c c ¯ c ¯ in the $$J/\Psi $$ J / Ψ -pair mass spectrum. In this work, we construct four scalar ($$J^{PC} = 0^{++}$$ J PC = 0 + + ) $$[8_c]_{Q\bar{Q^\prime }}\otimes [8_c]_{Q^\prime {\bar{Q}}}$$ [ 8 c ] Q Q ′ ¯ ⊗ [ 8 c ] Q ′ Q ¯ type currents to investigate the fully-heavy tetraquark state $$Q Q^\prime {\bar{Q}} \bar{Q^\prime }$$ Q Q ′ Q ¯ Q ′ ¯ in the framework of QCD sum rules, where $$Q=c, b$$ Q = c , b and $$Q^\prime = c, b$$ Q ′ = c , b . Our results suggest that the broad structure around 6.2-6.8 GeV can be interpreted as the $$0^{++}$$ 0 + + octet–octet tetraquark states with masses $$6.44\pm 0.11$$ 6.44 ± 0.11 GeV and $$6.52\pm 0.10$$ 6.52 ± 0.10 GeV, and the narrow structure around 6.9 GeV can be interpreted as the $$0^{++}$$ 0 + + octet–octet tetraquark states with masses $$6.87\pm 0.11$$ 6.87 ± 0.11 GeV and $$6.96\pm 0.11$$ 6.96 ± 0.11 GeV, respectively. Extending to the b-quark sector,the masses of their fully-bottom partners are found to be around 18.38-18.59 GeV. Additionally, we also analyze the spectra of the $$[8_c]_{c{\bar{c}}}\otimes [8_c]_{b {\bar{b}}}$$ [ 8 c ] c c ¯ ⊗ [ 8 c ] b b ¯ and $$[8_c]_{c{\bar{b}}}\otimes [8_c]_{b {\bar{c}}}$$ [ 8 c ] c b ¯ ⊗ [ 8 c ] b c ¯ tetraquark states, which lie in the range of 12.51–12.74 GeV and 12.49–12.81 GeV, respectively.


2021 ◽  
Vol 103 (5) ◽  
Author(s):  
D. Hatton ◽  
C. T. H. Davies ◽  
J. Koponen ◽  
G. P. Lepage ◽  
A. T. Lytle ◽  
...  

Author(s):  
F.A. Chishtie ◽  
D.G.C. McKeon ◽  
T.N. Sherry

We examine the perturbative calculation of the inclusive semi-leptonic decay rate \Gamma for the b-quark, using mass-independent renormalization. To finite order of perturbation theory the series for \Gamma will depend on the unphysical renormalization scale parameter μ and on the particular choice of mass-independent renormalization scheme; these dependencies will only be removed after summing the series to all orders. In this paper we show that all explicit μ-dependence of \Gamma, through powers of ln(μ), can be summed by using the renormalization group equation. We then find that this explicit μ-dependence can be combined together with the implicit μ-dependence of \Gamma (through powers of both the running coupling a(μ) and the running b-quark mass m(μ)) to yield a μ-independent perturbative expansion for \Gamma in terms of a(μ) and m(μ) both evaluated at a renormalization scheme independent mass scale IM which is fixed in terms of either the ``\overline{MS} mass'' \overline{m}_b of the b quark or its pole mass m_{pole}. At finite order the resulting perturbative expansion retains a degree of arbitrariness associated with the particular choice of mass-independent renormalization scheme. We use the coefficients c_i and g_i of the perturbative expansions of the renormalization group functions \beta(a) and \gamma(a), associated with a(μ) and m(μ) respectively, to characterize the remaining renormalization scheme arbitrariness of \Gamma. We further show that all terms in the expansion of \Gamma can be written in terms of the c_i and g_i coefficients and a set of renormalization scheme independent parameters \tau_i. A second set of renormalization scheme independent parameters \sigma_i is shown to play a very similar role in the perturbative expansion of m_{pole} in terms of m(μ) and a(μ). We illustrate our approach by a perturbative computation of \Gamma using the \overline{MS} renormalization scheme. Two other particular mass independent renormalization schemes are briefly considered.


2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
Alexander Lenz ◽  
Maria Laura Piscopo ◽  
Aleksey V. Rusov

Abstract We compute the Darwin operator contribution ($$ 1/{m}_b^3 $$ 1 / m b 3 correction) to the width of the inclusive non-leptonic decay of a B meson (B+, Bd or Bs), stemming from the quark flavour-changing transition b → $$ {q}_1{\overline{q}}_2{q}_3 $$ q 1 q ¯ 2 q 3 , where q1, q2 = u, c and q3 = d, s. The key ideas of the computation are the local expansion of the quark propagator in the external gluon field including terms with a covariant derivative of the gluon field strength tensor and the standard technique of the Heavy Quark Expansion (HQE). We confirm the previously known expressions of the $$ 1/{m}_b^3 $$ 1 / m b 3 contributions to the semi-leptonic decay b → $$ {q}_1\mathrm{\ell}{\overline{\nu}}_{\mathrm{\ell}} $$ q 1 ℓ ν ¯ ℓ , with ℓ = e, μ, τ and of the $$ 1/{m}_b^2 $$ 1 / m b 2 contributions to the non-leptonic modes. We find that this new term can give a sizeable correction of about −4 % to the non-leptonic decay width of a B meson. For Bd and Bs mesons this turns out to be the dominant correction to the free b-quark decay, while for the B+ meson the Darwin term gives the second most important correction — roughly 1/2 to 1/3 of the phase space enhanced Pauli interference contribution. Due to the tiny experimental uncertainties in lifetime measurements the incorporation of the Darwin term contribution is crucial for precision tests of the Standard Model.


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