First Observation of the DecayBs2*(5840)0→B*+

Abstract

The properties of the orbitally excited (L ¼ 1) B 0 s states are studied by using 1:0 fb À1 of pp collisions at ffiffi ffi s p ¼ 7 TeV collected with the LHCb detector. The first observation of the B Ã s2 ð5840Þ 0 meson decaying to B Ãþ K À is reported, and the corresponding branching fraction measured relative to the B þ K À decay mode. The B s1 ð5830Þ 0 ! B Ãþ K À decay is observed as well. The width of the B Ã s2 ð5840Þ 0 state is measured for the first time, and the masses of the two states are determined with the highest precision to date. The observation of the B Ã s2 ð5840Þ 0 ! B Ãþ K À decay favors the spin-parity assignment J P ¼ 2 þ for the B Ã s2 ð5840Þ 0 meson. In addition, the most precise measurement of the mass difference mðB Ãþ Þ À mðB þ Þ ¼ 45:01 AE 0:30ðstatÞ AE 0:23ðsystÞ MeV=c 2 is obtained. DOI: 10.1103/PhysRevLett.110.151803 PACS numbers: 13.25.Hw, 12.39.Hg, 14.40.Nd Heavy quark effective theory describes mesons with one heavy and one light quark where the heavy quark is assumed to have infinite mass [1]. It is an important tool for calculating meson properties which may be modified by physics beyond the standard model, such as CP violation in charm meson decays [2] or the mixing and lifetimes of B mesons [3]. It also predicts the properties of excited B and B 0 s mesons [4][5][6][7], and precise measurements of these properties are a sensitive test of the validity of the theory. Within heavy quark effective theory the B 0 s mesons are characterized by three quantum numbers: the relative orbital angular momentum L of the two quarks, the total angular momentum of the light quark j q ¼ jL AE 1 2 j, and the total angular momentum of the B 0 s meson J ¼ jj q AE 1 2 j. For L ¼ 1 there are four different possible (J, j q ) combinations, all with even parity. These are collectively termed the orbitally excited states. Such states can decay to B þ K À and/or B Ãþ K À (the inclusion of charge-conjugate states is implied throughout this Letter), depending on their quantum numbers and mass values. The two states with j q ¼ 1=2, named B Ã s0 and B 0 s1 , are expected to decay through an S-wave transition and to have a large Oð100 MeV=c 2 Þ decay width. In contrast, the two states with j q ¼ 3=2, named B s1 ð5830Þ 0 and B Ã s2 ð5840Þ 0 (henceforth B s1 and B Ã s2 for brevity), are expected to decay through a D-wave transition and to have a narrow Oð1 MeV=c 2 Þ decay width. Table I gives an overview of these states.In this Letter, a 1:0 fb À1 sample of data collected by the LHCb detector is used to search for the orbitally excited B 0 s mesons in the mass distribution of B þ K À pairs, where the B þ mesons are selected in the four decay modes:Two narrow peaks were observed in the B þ K À mass distribution by the CDF Collaboration [9]. Putatively, they are identified with the states of the j q ¼ 3=2 doublet expected in heavy quark effective theory [4] and are named B s1 and B Ã s2 . As the B s1 ! B þ K À decay is forbidden, one of the mass peaks observed is interpreted as the B s1 ! B Ãþ K À decay fol...

Isospin violating decays of positive parity $$B_s$$ B s mesons in HM $$\chi $$ χ PT

“…[5]. These authors determined the spectrum of B s 1P states and they found that the masses of B s1 (5830) 0 and B * s2 (5840) 0 agree very well with the experimental results [1][2][3][4]. They predicted also the existence of the spin zero positive parity state (J P = 0 + ) with the mass m B s0 = 5.711(13) (19) [10][11][12][22][23][24].…”

“…Two positive parity mesons B s states: the J P = 1 + state B s1 (5830) 0 and the J P = 2 + state B * s2 (5840) 0 were observed by the CDF and LHCb collaborations [1][2][3][4]. Recent lattice results [5,6], as well as other work [7][8][9][10][11][12][13][14][15], have indicated that the observed states are most likely members of the (1 + , 2 + ) doublet.…”

Spectroscopic assignments of the excited B-mesons

“…While the so-called exotic states not conforming to quark model states have received the bulk of the attention [2][3][4][5][6], states that appear to be conventional quark model states can provide a useful test of the continued utility of the quark model [7][8][9]. Over the last decade the D0 [10,11], CDF [12][13][14], LHCb [15,16] and CMS [17] hadron collider experiments have observed a number of excited bottom and bottom-strange mesons. We summarize the properties of these states in Table I where we quote the Particle Data Group (PDG) values, averaged over charge states [18].…”

Studies of $${\mathrm {B}} ^{*}_{{\mathrm {s}}2}(5840)^0 $$ B s 2 ∗ ( 5840 ) 0 and $${\mathrm {B}} _{{\mathrm {s}}1}(5830)^0 $$ B s 1 (

“…Orbitally excited states of the B 0 s meson were observed by the CDF and D0 Collaborations via the decays into B ( * )+ K − [3,4]. More recently, the LHCb Collaboration presented a more precise study of these states and observed the decay B * s2 (5840) 0 → B * + K − [5], favouring the spin-parity assignment J P = 2 + for the B * s2 (5840) 0 state. The CDF Collaboration subsequently presented a study of excited B meson states [6] that included measurements of the B ( * ) s1,2 → B ( * )+ K − decays.…”