Production of semi-inclusive doubly heavy baryons via top-quark decays

Abstract

In the paper, we present a detailed discussion on the semi-inclusive production of doubly heavy baryons (Ξ bc and Ξ bb ) through top-quark decay channel, t → Ξ bQ ′ +Q ′ +W + , within the framework of nonrelativistic QCD. In our calculations, the contributions from the intermediate diquark states, bc [ 3 S 1 ]3 /6 , bc [ 1 S 0 ]3 /6 , bb [ 1 S 0 ] 6 , and bb [ 3 S 1 ]3, have been taken into consideration. Main uncertainties from the heavy quark mass (m c , m b or m t ), the renormalization scale µ r , and the nonperturbative transition probability have been estimated. For a comparison, we also analyze the production of doubly heavy baryons under the approximate fragmentation function approach. Estimated at the LHC or a High Luminosity LHC with L =10 34−36 cm −2 s −1 , there will be about 2.25 × 10 4−6 events of Ξ bc and 9.49 × 10 2−4 events of Ξ bb produced in one operation year through top-quark decays. * Recently, the LHCb Collaboration of the CERN LHC announced its first observation of the doubly heavy baryon Ξ ++ cc [1] for the proton-proton center-of-mass collision energy of 13 TeV and an integrated luminosity of 1.7 f b −1 , confirming the success of the quark model [2][3][4][5]. However, there is still no explicit evidence on the doubly heavy baryons Ξ bc and Ξ bb (throughout the paper, we label them as Ξ bQ ′ , with Q ′ representing the heavy b or c quark, respectively). A careful study on the Ξ bQ ′ production shall be helpful for confirming whether enough baryon events can be produced and for further testing of the quark model and the nonrelativistic QCD (NRQCD) [6,7]. Here, Ξ bQ ′ stands for the doubly heavy baryon Ξ bQ ′ q , where q denotes the light u, d, or s quark, respectively. At present, various methods for the production of doubly heavy baryons have been analyzed in the literature, such as those via the e + e − collisions [8][9][10][11], the hadronic collisions [9,[12][13][14][15][16][17][18][19][20][21], the gamma gamma collisions [14,22], the photoproduction mechanisms [14,23,24], the heavy ion collisions [25,26], etc.It has been confirmed that sizable doubly heavy baryons can be produced at the LHC via the hadronic production mechanisms; their production properties can be simulated by using a dedicated generator GENXICC [17,18,20]. In this paper, we shall discuss the production of doubly heavy baryons Ξ bQ ′ via the top-quark decays at the LHC or its successor [the High Luminosity LHC (HL-LHC)]. Because of the advantage of high luminosity and high energy, the LHC has already become a huge "top factory". For example, when the luminosity is up to 10 34 ∼ 10 36 cm −2 s −1 , there will be about 10 8 ∼ 10 10 tt pairs produced in one operation year at the LHC [27,28]. Thus, the top-quark decays will be a potentially good platform for studying the indirect production mechanism of the doubly heavy baryons and for searching the undetected Ξ bQ ′ . The decay width of the top quark is expected to be dominated by the process t → bW + . Thus, in the following, we shall study the production of doubly heav...

Excited doubly heavy baryon production via $W^+$ boson decays

“…Although there are no new doubly heavy baryons found yet, the discovery of Ξ ++ cc certainly inspires people's great interest in further researches on them. As to the theoretical aspect, some papers concentrate on the direct production of the doubly heavy baryon at e + e − colliders [28,29], the indirect production in the decay of Higgs or top quark [30,31], and hardronic production [32][33][34].…”

Production of doubly heavy baryons via Higgs boson decays

“…To study all possible production mechanisms of doubly heavy baryons shall be helpful for better understanding their properties and shall be a verification of the quark model and nonrelativistic Quantum Chromodynamics (NRQCD) [16,17]. There were some analyses of the direct/indirect production of doubly heavy baryons through e + e − colliders [18][19][20][21], hadronic production [19,[22][23][24][25][26][27][28][29][30][31], gamma-gamma production [24,32], photoproduction [24,33,34], heavy ion collisions [35,36], top quark decays [37], etc.…”

“…In addition, the transition probability h3 can be approximatively related to the Schrödinger wave function at the origin |Ψ QQ ′ (0)| for the S-wave states, while there is a relatively larger uncertainty for the transition probability h 6 , which has been analyzed detailedly in Ref. [37]. For convenience, we set h 6 ≃ h3 = |Ψ QQ ′ (0)| 2 [17,42] as an approximate estimate.…”

Effects of a dense medium on parameters of doubly heavy baryons

“…We hope that, by the development of experimental facilities, we will be able to detect other members of the doubly heavy baryons. The production mechanism of doubly heavy baryons has an important place in the literature [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36]. Naturally, a doubly heavy baryon can be produced using a two-step procedure: i-) in a hard interaction, a double heavy diquark is produced pertur-batively, ii-) and then it is transformed to the baryon within the soft hadronization process [34].…”