|
|
Alioli, S., Fuster, J., Garzelli, M. V., Gavardi, A., Irles, A., Melini, D., et al. (2022). Phenomenology of t(t)over-barj plus X production at the LHC. J. High Energy Phys., 05(5), 146–63pp.
Abstract: We present phenomenological results for t (t) over barj + X production at the Large Hadron Collider, of interest for designing forthcoming experimental analyses of this process. We focus on those cases where the t (t) over barj + X process is considered as a signal. We discuss present theoretical uncertainties and the dependence on relevant input parameters entering the computation. For the R. distribution, which depends on the invariant mass of the t (t) over barj-system, we present reference predictions in the on-shell, (MS) over bar and MSR top-quark mass renormalization schemes, applying the latter scheme to this process for the first time. Our conclusions are particularly interesting for those analyses aiming at extracting the topquark mass from cross-section measurements.
|
|
|
|
Buchta, S., Chachamis, G., Draggiotis, P., Malamos, I., & Rodrigo, G. (2014). On the singular behaviour of scattering amplitudes in quantum field theory. J. High Energy Phys., 11(11), 014–13pp.
Abstract: We analyse the singular behaviour of one-loop integrals and scattering amplitudes in the framework of the loop-tree duality approach. We show that there is a partial cancellation of singularities at the loop integrand level among the different components of the corresponding dual representation that can be interpreted in terms of causality. The remaining threshold and infrared singularities are restricted to a finite region of the loop momentum space, which is of the size of the external momenta and can be mapped to the phase-space of real corrections to cancel the soft and collinear divergences.
|
|
|
|
LHCb Collaboration(Aaij, R. et al), Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2021). Observation of the decay Lambda b0 -> chi(c1)p pi(-). J. High Energy Phys., 05(5), 095–21pp.
Abstract: The Cabibbo-suppressed decay Lambda b0</mml:msubsup>-> chi (c1)p(-) is observed for the first time using data from proton-proton collisions corresponding to an integrated luminosity of 6 fb(-1), collected with the LHCb detector at a centre-of-mass energy of 13 TeV. Evidence for the Lambda b0</mml:msubsup>-> chi (c2)p(-) decay is also found. Using the Lambda b0</mml:msubsup>-> chi (c1)pK(-) decay as normalisation channel, the ratios of branching fractions are measured to be<disp-formula id=“Equa”><mml:mtable displaystyle=“true”><mml:mtr><mml:mtd><mml:mfrac>B<mml:mfenced close=“)” open=“(”>Lambda b0</mml:msubsup>-> chi c1p pi-</mml:mfenced>B<mml:mfenced close=“)” open=“(”>Lambda b0</mml:msubsup>-> <mml:msub>chi c1pK-</mml:mfenced></mml:mfrac>=<mml:mfenced close=“)” open=“(”>6.59 +/- 1.01 +/- 0.22</mml:mfenced>x10-2,</mml:mtd></mml:mtr><mml:mtr><mml:mtd><mml:mfrac>B<mml:mfenced close=“)” open=“(”>Lambda b0 -> <mml:msub>chi c2p pi-</mml:mfenced>B<mml:mfenced close=“)” open=“(”>Lambda b0 -> <mml:msub>chi c1p pi-</mml:mfenced></mml:mfrac>=0.95 +/- 0.30 +/- 0.04 +/- 0.04,</mml:mtd></mml:mtr><mml:mtr><mml:mtd><mml:mfrac>B<mml:mfenced close=“)” open=“(”>Lambda b0 -> <mml:msub>chi c2pK-</mml:mfenced>B<mml:mfenced close=“)” open=“(”>Lambda b0 -> <mml:msub>chi c1pK-</mml:mfenced></mml:mfrac>=1.06 +/- 0.05 +/- 0.04 +/- 0.04,</mml:mtd></mml:mtr></mml:mtable><graphic position=“anchor” xmlns:xlink=“http://www.w3.org/1999/xlink” xlink:href=“13130 202115658 ArticleEqua.gif”></graphic></disp-formula><p id=“Par2”>where the first uncertainty is statistical, the second is systematic and the third is due to the uncertainties in the branching fractions of chi (c1,2)-> J/psi gamma decays.<fig id=“Figa” position=“anchor”><graphic position=“anchor” specific-use=“HTML” mime-subtype=“JPEG” xmlns:xlink=“http://www.w3.org/1999/xlink” xlink:href=“MediaObjects/13130 202115658 FigaHTML.jpg” id=“MO1”></graphic
|
|
|
|
LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2016). Observation of the B (s) (0) -> J/psi phi phi decay. J. High Energy Phys., 03(3), 040–18pp.
Abstract: The B (s) (0) -> J/psi phi phi decay is observed in pp collision data corresponding to an integrated luminosity of 3 fb(-1) recorded by the LHCb detector at centre-of-mass energies of 7 TeV and 8 TeV. This is the first observation of this decay channel, with a statistical significance of 15 standard deviations. The mass of the B (s) (0) meson is measured to be 5367.08 +/- 0.38 +/- 0.15 MeV/c(2). The branching fraction ratio B[B(s)(0) -> J/psi phi phi]/B[B(s)(0) -> J/psi phi] is measured to be 0.0115 +/- 0.0012 (- 0.0009) (+ 0.0005) . In both cases, the first uncertainty is statistical and the second is systematic. No evidence for non-resonant B(s)(0) -> J/psi phi K (+) K (-) or B(s)(0) -> J/psi K (+) K (-) K (+) K (-) decays is found.
|
|
|
|
LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., et al. (2020). Observation of structure in the J/psi-pair mass spectrum. Sci. Bull., 65(23), 1983–1993.
Abstract: Using proton-proton collision data at centre-of-mass energies of root s = 7, 8 and 13 TeV recorded by the LHCb experiment at the Large Hadron Collider, corresponding to an integrated luminosity of 9 fb(-1), the invariant mass spectrum of J/psi pairs is studied. A narrow structure around 6.9 GeV/c(2) matching the line-shape of a resonance and a broad structure just above twice the J/psi mass are observed. The deviation of the data from nonresonant J/psi-pair production is above five standard deviations in the mass region between 6.2 and 7.4 GeV/c(2), covering predicted masses of states composed of four charm quarks. The mass and natural width of the narrow X(6900) structure are measured assuming a Breit-Wigner lineshape.
|
|
