Effects of vector leptoquarks on $\Lambda_b \rightarrow \Lambda_c \ell \overline{\nu}_\ell$ decay

• Experimental data on $R(D^{(*)})$, $R(K^{(*)})$ and $R(J/\psi)$, provided by different collaborations, show sizable deviations from the standard model (SM) predictions. To describe these anomalies many new physics scenarios have been proposed. One of them is leptoquark model with introducing the vector and scalar leptoquarks coupling simultaneously to the quarks and leptons. To look for similar possible anomalies in baryonic sector, we investigate the effects of a vector leptoquark $U_3 (3,3, \frac{2}{3})$ on various physical quantities related to the tree-level $\Lambda_b \rightarrow \Lambda_c \ell ~ \overline{\nu}_\ell$ decays ($\ell=\mu, ~\tau$), which proceed via $b \rightarrow c~\ell ~ \overline{\nu}_\ell$ transitions at quark level. We calculate the differential branching ratio, forward-backward asymmetry and longitudinal polarizations of lepton and $\Lambda_{c}$ baryon at $\mu$ and $\tau$ lepton channels in leptoquark model and compare their behavior with respect to $q^2$ with the predictions of the SM. In the calculations we use the form factors calculated in full QCD as the main inputs and take into account all the errors coming from the form factors and model parameters. It is observed that, at $\tau$ channel, the $R_A$ fit solution to data related to the leptoquark model sweeps some regions out of the SM band but it has a considerable intersection with the SM predictions. The $R_B$ type solution gives roughly the same results with the those of the SM on $DBR(q^2)-q^2$. At $\mu$ channel, the leptoquark model gives consistent results with the SM predictions and existing experimental data on the behavior of $DBR(q^2)$ with respect to $q^2$. As far as the $q^2$ behavior of the $A_{FB}(q^2)$ is concerned, the two types of fits in leptoquark model for $\tau$ and the predictions of this model at $\mu$ channel give exactly the same results as the SM. We also investigate the behavior of the parameter $R(q^2)$ with respect to $q^2$ and the value of $R(\Lambda_c)$ both in vector leptoquark and SM models. Both types fit solutions lead to results that deviate considerably from the SM predictions on $R(q^2)- q^2$ as well as $R(\Lambda_c)$. Future experimental data on $R(q^2)- q^2$ as well as $R(\Lambda_c)$, which would be available after measurements on $\Lambda_b \rightarrow \Lambda_c \tau ~ \overline{\nu}_\tau$ channel, will be very helpful. Any experimental deviations from the SM predictions in this channel will strengthen the importance of the tree-level hadronic weak transitions as good probes of the new physics effects beyond the SM (BSM).
•  [1] Y. S. Amhis et al [HFLAV Collaboration], arXiv: 1909.12524[hep-ex] [2] R. Aaij et al. [LHCb Collaboration], Phys. Rev. Lett. 113, 151601 (2014), arXiv:1406.6482[hep-ex [3] R. Aaij et al. [LHCb Collaboration], JHEP 1708, 055 (2017), arXiv:1705.05802[hep-ex [4] M. Bordone, G. Isidori, and A. Pattori, Eur. Phys. J. C 76(8), 440 (2016), arXiv:1605.07633[hep-ph [5] S. Descotes-Genon, L. Hofer, J. Matias et al., JHEP 1606, 092 (2016), arXiv:1510.04239[hep-ph [6] R. Aaij et al. [LHCb Collaboration], Phys. Rev. Lett. 120(12), 121801 (2018), arXiv:1711.05623[hep-ex [7] T. D. Cohen, H. Lamm, and R. F. Lebed, JHEP 1809, 168 (2018), arXiv:1807.02730[hep-ph [8] Z. Rui, H. Li, G. x. Wang et al., Eur. Phys. J. C 76(10), 564 (2016), arXiv:1602.08918[hep-ph [9] R. Dutta and A. Bhol, Phys. Rev. D 96(7), 076001 (2017), arXiv:1701.08598[hepph [10] D. Leljak, B. Melic, and M. Patra, JHEP 1905, 094 (2019), arXiv:1901.08368[hep-ph [11] C. W. Murphy and A. Soni, Phys. Rev. D 98(9), 094026 (2018), arXiv:1808.05932[hep-ph [12] W. F. Wang, Y. Y. Fan, and Z. J. Xiao, Chin. Phys. C 37, 093102 (2013), arXiv:1212.5903[hep-ph [13] K. Azizi, Y. Sarac, and H. Sundu, Phys. Rev. D 99(11), 113004 (2019), arXiv:1904.08267[hep-ph [14] A. Issadykov and M. A. Ivanov, Phys. Lett. B 783, 178 (2018), arXiv:1804.00472[hep-ph [15] T. Huang and F. Zuo, Eur. Phys. J. C 51, 833 (2007) [16] V. V. Kiselev, hep-ph/0211021 [17] M. A. Ivanov, J. G. Korner, and P. Santorelli, Phys. Rev. D 73, 054024 (2006) [18] W. Wang, Y. L. Shen, and C. D. Lu, Phys. Rev. D 79, 054012 (2009), arXiv:0811.3748[hep-ph [19] X. Q. Hu, S. P. Jin, and Z. J. Xiao, arXiv: 1904.07530[hep-ph] [20] Z. R. Huang, Y. Li, C. D. Lu et al., Phys. Rev. D 98(9), 095018 (2018), arXiv:1808.03565[hep-ph [21] A. Berns and H. Lamm, JHEP 1812, 114 (2018), arXiv:1808.07360[hep-ph [22] M. Blanke, A. Crivellin, T. Kitahara et al., Phys. Rev. D 100(3), 035035 (2019), arXiv:1905.08253[hep-ph [23] K. Azizi and J. Y. Sungu, Phys. Rev. D 97(7), 074007 (2018), arXiv:1803.02085[hep-ph [24] W. Buchmuller, R. Ruckl, and D. Wyler, Phys. Lett. B 191, 442(1987) Erratum: [Phys. Lett. B 448, 320(1999)] [25] I. Dorner, S. Fajfer, A. Greljo et al., Phys. Rept. 641, 1 (2016), arXiv:1603.04993[hep-ph [26] B. Schrempp and F. Schrempp, Phys. Lett. B 153, 101 (1985) [27] J. Wudka, Phys. Lett. B 167, 337 (1986) [28] J. C. Pati and A. Salam, Phys. Rev. D 10(1974) 275 Erratum: [Phys. Rev. D 11(1975) 703] [29] H. Georgi and S. L. Glashow, Phys. Rev. Lett. 32, 438 (1974) [30] H. Georgi, AIP Conf. Proc. 23, 575 (1975) [31] A. Angelescu, D. Beirevi, D. A. Faroughy et al., JHEP 1810, 183 (2018), arXiv:1808.08179[hep-ph [32] J. Zhang, J. Su, and Q. Zeng, Nucl. Phys. B 938, 131 (2019) [33] S. Fajfer and N. Konik, Phys. Lett. B 755, 270 (2016), arXiv:1511.06024[hep-ph [34] X. Q. Li, Y. D. Yang, and X. Zhang, JHEP 1702, 068 (2017), arXiv:1611.01635[hep-ph [35] J. Zhang, C. X. Yue, C. H. Li et al., arXiv: 1905.04074[hep-ph] [36] S. Sahoo and R. Mohanta, J. Phys. G 45(8), 085003 (2018), arXiv:1806.01048[hep-ph [37] N. Assad, B. Fornal, and B. Grinstein, Phys. Lett. B 777, 324 (2018), arXiv:1708.06350[hep-ph [38] M. Blanke and A. Crivellin, Phys. Rev. Lett. 121(1), 011801 (2018), arXiv:1801.07256[hep-ph [39] L. Calibbi, A. Crivellin, and T. Li, Phys. Rev. D 98(11), 115002 (2018), arXiv:1709.00692[hep-ph [40] S. Sahoo, R. Mohanta, and A. K. Giri, Phys. Rev. D 95(3), 035027 (2017), arXiv:1609.04367[hepph [41] A. Kadeer, J. G. Korner, and U. Moosbrugger, Eur. Phys. J. C 59, 2747 (2009) [42] P. Bialas, J. G. Korner, M. Kramer et al., Z. Phys. C 57, 115134 (1993) [43] R. Aaij et al. [LHCb], Phys. Lett. B 724, 27-35 (2013), arXiv:1302.5578[hep-ex [44] M. Freytsis, Z. Ligeti, and J. T. Ruderman, Phys. Rev. D 92(5), 054018 (2015), arXiv:1506.08896[hep-ph [45] X. Mu, Y. Li, Z. Zou et al., Phys. Rev. D 100(11), 113004 (2019), arXiv:1909.10769[hep-ph [46] S. Chatrchyan et al. [CMS Collaboration], Phys. Rev. Lett. 110(8), 081801 (2013), arXiv:1210.5629[hep-ex [47] A. M. Sirunyan et al. [CMS Collaboration], J. High Energy Phys. 1807, 115 (2018) [48] T. Gutsche, M. A. Ivanov, J. G. Krner et al., Phys. Rev. D 91(7), 074001(2015) Erratum: [Phys. Rev. D 91(11),119907(2015)] [arXiv: 1502.04864[hep-ph]] [49] S. Shivashankara, W. Wu, and A. Datta, Phys. Rev. D 91(11), 115003 (2015), arXiv:1502.07230[hep-ph [50] R. Dutta, Phys. Rev. D 93(5), 054003 (2016), arXiv:1512.04034[hep-ph [51] Q. Y. Hu, X. Q. Li, and Y. D. Yang, Eur. Phys. J. C 79(3), 264 (2019), arXiv:1810.04939[hep-ph [52] C. Patrignani et al. [Particle Data Group], Phys. Rev. D 98, 030001(2018) and 2019 update [53] R. Aaij et al. [LHCb Collaboration], Phys. Rev. D 96(11), 112005 (2017), arXiv:1709.01920[hep-ex

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K. Azizi, A. T. Olgun and Z. Tavukoğlu. Effects of vector leptoquarks on $\Lambda_b \rightarrow \Lambda_c \ell \overline{\nu}_\ell$ decay[J]. Chinese Physics C.
K. Azizi, A. T. Olgun and Z. Tavukoğlu. Effects of vector leptoquarks on $\Lambda_b \rightarrow \Lambda_c \ell \overline{\nu}_\ell$ decay[J]. Chinese Physics C.
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沈阳化工大学材料科学与工程学院 沈阳 110142

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Effects of vector leptoquarks on $\Lambda_b \rightarrow \Lambda_c \ell \overline{\nu}_\ell$ decay

• 1. Department of Physics, University of Tehran, North Karegar Avenue, Tehran 14395-547, Iran
Abstract: Experimental data on $R(D^{(*)})$, $R(K^{(*)})$ and $R(J/\psi)$, provided by different collaborations, show sizable deviations from the standard model (SM) predictions. To describe these anomalies many new physics scenarios have been proposed. One of them is leptoquark model with introducing the vector and scalar leptoquarks coupling simultaneously to the quarks and leptons. To look for similar possible anomalies in baryonic sector, we investigate the effects of a vector leptoquark $U_3 (3,3, \frac{2}{3})$ on various physical quantities related to the tree-level $\Lambda_b \rightarrow \Lambda_c \ell ~ \overline{\nu}_\ell$ decays ($\ell=\mu, ~\tau$), which proceed via $b \rightarrow c~\ell ~ \overline{\nu}_\ell$ transitions at quark level. We calculate the differential branching ratio, forward-backward asymmetry and longitudinal polarizations of lepton and $\Lambda_{c}$ baryon at $\mu$ and $\tau$ lepton channels in leptoquark model and compare their behavior with respect to $q^2$ with the predictions of the SM. In the calculations we use the form factors calculated in full QCD as the main inputs and take into account all the errors coming from the form factors and model parameters. It is observed that, at $\tau$ channel, the $R_A$ fit solution to data related to the leptoquark model sweeps some regions out of the SM band but it has a considerable intersection with the SM predictions. The $R_B$ type solution gives roughly the same results with the those of the SM on $DBR(q^2)-q^2$. At $\mu$ channel, the leptoquark model gives consistent results with the SM predictions and existing experimental data on the behavior of $DBR(q^2)$ with respect to $q^2$. As far as the $q^2$ behavior of the $A_{FB}(q^2)$ is concerned, the two types of fits in leptoquark model for $\tau$ and the predictions of this model at $\mu$ channel give exactly the same results as the SM. We also investigate the behavior of the parameter $R(q^2)$ with respect to $q^2$ and the value of $R(\Lambda_c)$ both in vector leptoquark and SM models. Both types fit solutions lead to results that deviate considerably from the SM predictions on $R(q^2)- q^2$ as well as $R(\Lambda_c)$. Future experimental data on $R(q^2)- q^2$ as well as $R(\Lambda_c)$, which would be available after measurements on $\Lambda_b \rightarrow \Lambda_c \tau ~ \overline{\nu}_\tau$ channel, will be very helpful. Any experimental deviations from the SM predictions in this channel will strengthen the importance of the tree-level hadronic weak transitions as good probes of the new physics effects beyond the SM (BSM).