scholarly journals Study of the doubly charmed tetraquark $T_{cc}^+$

2021 ◽  
Author(s):  
Ivan Belyaev
Keyword(s):  
D Mesons ◽  
Scattering Length ◽  
Pole Position ◽  
Data Set ◽  
Proton Proton ◽  
Proton Collisions ◽  
Quantum Numbers ◽  
Lhcb Detector ◽  
Narrow State ◽  
Proton Proton Collisions

Abstract An exotic narrow state in the D0D0π + mass spectrum just below the D∗+D0 mass threshold is studied using a data set corresponding to an integrated luminosity of 9 fb−1 acquired with the LHCb detector in proton-proton collisions at centre-of-mass energies of 7, 8 and 13 TeV. The state is consistent with the ground isoscalar T+ cc tetraquark with a quark content of ccud and spin-parity quantum numbers JP = 1+. Study of the DD mass spectra disfavours interpretation of the resonance as the isovector state. The decay structure via intermediate off-shell D∗+ mesons is confirmed by the D0π + mass distribution. The mass of the resonance and its coupling to the D∗D system are analysed. Resonance parameters including the pole position, scattering length, effective range and compositeness are measured to reveal important information about the nature of the T+ cc state. In addition, an unexpected dependence of the production rate on track multiplicity is observed.

scholarly journals Study of $$ {\mathrm{B}}_{\mathrm{s}}^0 $$ → J/ψπ+π−K+K− decays

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
R. Aaij ◽  
◽  
C. Abellán Beteta ◽  
T. Ackernley ◽  
B. Adeva ◽  
...  
Keyword(s):  
Branching Fractions ◽  
Centre Of Mass ◽  
Single Measurement ◽  
Data Set ◽  
Proton Proton ◽  
Proton Collisions ◽  
A Value ◽  
Lhcb Detector ◽  
First Time ◽  
Proton Proton Collisions

Abstract The decays $$ {\mathrm{B}}_{\mathrm{s}}^0 $$ B s 0 → J/ψπ+π−K+K− are studied using a data set corresponding to an integrated luminosity of 9 fb−1, collected with the LHCb detector in proton-proton collisions at centre-of-mass energies of 7, 8 and 13 TeV. The decays $$ {\mathrm{B}}_{\mathrm{s}}^0 $$ B s 0 → $$ \mathrm{J}/{\uppsi \mathrm{K}}^{\ast 0}{\overline{\mathrm{K}}}^{\ast 0} $$ J / ψK ∗ 0 K ¯ ∗ 0 and $$ {\mathrm{B}}_{\mathrm{s}}^0 $$ B s 0 → χc1(3872)K+K−, where the K+K−pair does not originate from a ϕ meson, are observed for the first time. Precise measurements of the ratios of branching fractions between intermediate χc1(3872)ϕ, $$ \mathrm{J}/{\uppsi \mathrm{K}}^{\ast 0}{\overline{\mathrm{K}}}^{\ast 0} $$ J / ψK ∗ 0 K ¯ ∗ 0 , ψ(2S)ϕ and χc1(3872)K+K− states are reported. A structure, denoted as X(4740), is observed in the J/ψϕ mass spectrum and, assuming a Breit-Wigner parameterisation, its mass and width are determined to be$$ {\displaystyle \begin{array}{c}{m}_{\mathrm{X}(4740)}=4741\pm 6\pm 6\kern0.5em \mathrm{MeV}/{c}^2,\\ {}{\Gamma}_{\mathrm{X}(4740)}=53\pm 15\pm 11\kern0.5em \mathrm{MeV},\end{array}} $$ m X 4740 = 4741 ± 6 ± 6 MeV / c 2 , Γ X 4740 = 53 ± 15 ± 11 MeV , where the first uncertainty is statistical and the second is systematic. In addition, the most precise single measurement of the mass of the $$ {\mathrm{B}}_{\mathrm{s}}^0 $$ B s 0 meson is performed and gives a value of$$ {m}_{{\mathrm{B}}_{\mathrm{s}}^0}=5366.98\pm 0.07\pm 0.13\kern0.5em \mathrm{MeV}/{c}^2. $$ m B s 0 = 5366.98 ± 0.07 ± 0.13 MeV / c 2 .

Models prediction of hadrons production ratios in pp collisions at s = 7 TeV

2019 ◽  
Vol 34 (13) ◽  
pp. 1950090 ◽  
Author(s):  
M. Ajaz ◽  
M. Bilal ◽  
Y. Ali ◽  
M. K. Suleymanov ◽  
K. H. Khan
Keyword(s):  
Experimental Data ◽  
Transverse Momentum ◽  
Charged Particles ◽  
Hadron Production ◽  
Proton Proton ◽  
Proton Collisions ◽  
Particle Ratios ◽  
Production Models ◽  
Lhcb Detector ◽  
Proton Proton Collisions

The pseudorapidity [Formula: see text] dependence of charged-particles ratios in three transverse momentum [Formula: see text] regions, obtained by hadron production models, in proton–proton collisions at 7 TeV are compared with the measurements of LHCb detector. Compared to the experimental data, the [Formula: see text] ratios are independent of [Formula: see text] and [Formula: see text] and are very well predicted by all models (DPMJETIII, EPOS1.99, EPOS-LHC, HIJING1.383, QGSJETII-04 and Sibyll2.3c). All models predict the [Formula: see text] ratio at low [Formula: see text] for [Formula: see text], but underestimate afterward while reproducing the experimental data at medium and high [Formula: see text] very well. The [Formula: see text] ratio is described by the models very well at high [Formula: see text] in the low and medium [Formula: see text] region. At high [Formula: see text], models predict the experimental data well, except Sibyll2.3c that slightly overestimates. The [Formula: see text] ratio is predicted by EPOS1.99, HIJING and Sibyll at low [Formula: see text] and EPOS-LHC, EPOS1.99 and Sibyll predicted at high [Formula: see text] for low [Formula: see text]. For medium [Formula: see text], EPOS1.99 and Sibyll predict very well for [Formula: see text] while EPOS-LHC and HIJING models reproduce the data for [Formula: see text]. All models underpredict the [Formula: see text] ratio for [Formula: see text]. For the [Formula: see text] and [Formula: see text] ratios, only Sibyll and EPOS1.99 models could reproduce some regions of [Formula: see text] and [Formula: see text]. None of the models satisfactorily predict all the ratios. the same particle ratios are well described by most of the models while the discrepancies occur mostly in predicting the different particles ratios.

scholarly journals Measurement of Longitudinal Spin Asymmetries for Weak Boson Production in Polarized Proton-Proton Collisions at STAR

2016 ◽  
Vol 40 ◽  
pp. 1660019
Author(s):  
Jinlong Zhang
Keyword(s):  
Spin Asymmetry ◽  
Data Set ◽  
Proton Proton ◽  
Weak Boson ◽  
Spin Asymmetries ◽  
Proton Collisions ◽  
Double Spin ◽  
Polarized Proton ◽  
The Status ◽  
Proton Proton Collisions

The production of [Formula: see text] bosons in longitudinally polarized [Formula: see text] collisions is a powerful tool to study the spin-flavor structure of the proton. We report measurements of single- and double-spin asymmetries for [Formula: see text] and [Formula: see text] production in longitudinally polarized proton-proton collisions at [Formula: see text] GeV at RHIC. The single-spin asymmetry results for [Formula: see text] from data sets collected by STAR experiment in 2011 and 2012 provided new constraints on proton’s polarized sea quark distributions and prefer a sizable value for [Formula: see text] polarization. The status for the analysis of a much larger data set collected by STAR in 2013 will also be given.

scholarly journals Observation of the decay $$ {\Lambda}_{\mathrm{b}}^0 $$ → χc1pπ−

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
R. Aaij ◽  
◽  
C. Abellán Beteta ◽  
T. Ackernley ◽  
B. Adeva ◽  
...  
Keyword(s):  
Branching Fractions ◽  
Centre Of Mass ◽  
Mass Energy ◽  
Proton Proton ◽  
Proton Collisions ◽  
Lhcb Detector ◽  
Using Data ◽  
Cabibbo Suppressed ◽  
First Time ◽  
Proton Proton Collisions

Abstract The Cabibbo-suppressed decay $$ {\Lambda}_{\mathrm{b}}^0 $$ Λ b 0 → χc1pπ− 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 $$ {\Lambda}_{\mathrm{b}}^0 $$ Λ b 0 → χc2pπ− decay is also found. Using the $$ {\Lambda}_{\mathrm{b}}^0 $$ Λ b 0 → χc1pK− decay as normalisation channel, the ratios of branching fractions are measured to be$$ {\displaystyle \begin{array}{c}\frac{\mathcal{B}\left({\Lambda}_{\mathrm{b}}^0\to {\upchi}_{\mathrm{c}1}{\mathrm{p}\uppi}^{-}\right)}{\mathcal{B}\left({\Lambda}_{\mathrm{b}}^0\to {\upchi}_{\mathrm{c}1}{\mathrm{p}\mathrm{K}}^{-}\right)}=\left(6.59\pm 1.01\pm 0.22\right)\times {10}^{-2},\\ {}\frac{\mathcal{B}\left({\Lambda}_{\mathrm{b}}^0\to {\upchi}_{\mathrm{c}2}{\mathrm{p}\uppi}^{-}\right)}{\mathcal{B}\left({\Lambda}_{\mathrm{b}}^0\to {\upchi}_{\mathrm{c}1}{\mathrm{p}\uppi}^{-}\right)}=0.95\pm 0.30\pm 0.04\pm 0.04,\\ {}\frac{\mathcal{B}\left({\Lambda}_{\mathrm{b}}^0\to {\upchi}_{\mathrm{c}2}{\mathrm{p}\mathrm{K}}^{-}\right)}{\mathcal{B}\left({\Lambda}_{\mathrm{b}}^0\to {\upchi}_{\mathrm{c}1}{\mathrm{p}\mathrm{K}}^{-}\right)}=1.06\pm 0.05\pm 0.04\pm 0.04,\end{array}} $$ B Λ b 0 → χ c 1 pπ − B Λ b 0 → χ c 1 pK − = 6.59 ± 1.01 ± 0.22 × 10 − 2 , B Λ b 0 → χ c 2 pπ − B Λ b 0 → χ c 1 pπ − = 0.95 ± 0.30 ± 0.04 ± 0.04 , B Λ b 0 → χ c 2 pK − B Λ b 0 → χ c 1 pK − = 1.06 ± 0.05 ± 0.04 ± 0.04 , where the first uncertainty is statistical, the second is systematic and the third is due to the uncertainties in the branching fractions of χc1,2→ J/ψγ decays.

scholarly journals Observation of new excited $${B} ^0_{s} $$ states

2021 ◽  
Vol 81 (7) ◽  
Author(s):  
◽  
R. Aaij ◽  
C. Abellán Beteta ◽  
T. Ackernley ◽  
B. Adeva ◽  
...  
Keyword(s):  
Production Cross ◽  
Branching Fraction ◽  
Total Production ◽  
Proton Proton ◽  
Proton Collisions ◽  
New States ◽  
Lhcb Detector ◽  
The Masses ◽  
Proton Proton Collisions ◽  
S States

AbstractA structure is observed in the $${B} ^{\pm }{K} ^{\mp }$$ B ± K ∓ mass spectrum in a sample of proton–proton collisions at centre-of-mass energies of 7, 8, and 13 TeV, collected with the LHCb detector and corresponding to a total integrated luminosity of 9$$\,\text {fb} ^{-1}$$ fb - 1 . The structure is interpreted as the result of overlapping excited $${B} ^0_{s} $$ B s 0 states. With high significance, a two-peak hypothesis provides a better description of the data than a single resonance. Under this hypothesis the masses and widths of the two states, assuming they decay directly to $${B} ^{\pm }{K} ^{\mp }$$ B ± K ∓ , are determined to be $$\begin{aligned} m_1&= 6063.5 \pm 1.2 \text { (stat)} \pm 0.8\text { (syst)}\,\text {Me}\text {V}, \\ \Gamma _1&= 26 \pm 4 \text { (stat)} \pm 4\text { (syst)}\,\text {Me}\text {V}, \\ m_2&= 6114 \pm 3 \text { (stat)} \pm 5\text { (syst)}\,\text {Me}\text {V}, \\ \Gamma _2&= 66 \pm 18 \text { (stat)} \pm 21\text { (syst)}\,\text {Me}\text {V}. \end{aligned}$$ m 1 = 6063.5 ± 1.2 (stat) ± 0.8 (syst) Me , Γ 1 = 26 ± 4 (stat) ± 4 (syst) Me , m 2 = 6114 ± 3 (stat) ± 5 (syst) Me , Γ 2 = 66 ± 18 (stat) ± 21 (syst) Me . Alternative values assuming a decay through $${B} ^{*\pm }{K} ^{\mp }$$ B ∗ ± K ∓ , with a missing photon from the $$B^{*\pm } \rightarrow B^{\pm }\gamma $$ B ∗ ± → B ± γ decay, which are shifted by approximately 45$$\,\text {Me}$$ Me V, are also determined. The possibility of a single state decaying in both channels is also considered. The ratio of the total production cross-section times branching fraction of the new states relative to the previously observed $$B_{s2}^{*0}$$ B s 2 ∗ 0 state is determined to be $$0.87 \pm 0.15 \text { (stat)} \pm 0.19 \text { (syst)}$$ 0.87 ± 0.15 (stat) ± 0.19 (syst) .

scholarly journals Precise determination of the $$B_{\mathrm{s}}^0$$–$$\overline B_{\mathrm{s}}^0$$ oscillation frequency

2022 ◽  
Author(s):  
◽  
R. Aaij ◽  
C. Abellán Beteta ◽  
T. Ackernley ◽  
B. Adeva ◽  
...  
Keyword(s):  
Oscillation Frequency ◽  
Strange Quark ◽  
Mass Difference ◽  
Hadron Collider ◽  
Precise Determination ◽  
Proton Proton ◽  
Proton Collisions ◽  
Lhcb Detector ◽  
Proton Proton Collisions

AbstractMesons comprising a beauty quark and strange quark can oscillate between particle ($${B}_{\mathrm{s}}^{0}$$ B s 0 ) and antiparticle ($${\overline{B}}_{\mathrm{s}}^{0}$$ B ¯ s 0 ) flavour eigenstates, with a frequency given by the mass difference between heavy and light mass eigenstates, Δms. Here we present a measurement of Δms using $${B}_{\mathrm{s}}^{0}\to {D}_{\mathrm{s}}^{-}$$ B s 0 → D s − π+ decays produced in proton–proton collisions collected with the LHCb detector at the Large Hadron Collider. The oscillation frequency is found to be Δms = 17.7683 ± 0.0051 ± 0.0032 ps−1, where the first uncertainty is statistical and the second is systematic. This measurement improves on the current Δms precision by a factor of two. We combine this result with previous LHCb measurements to determine Δms = 17.7656 ± 0.0057 ps−1, which is the legacy measurement of the original LHCb detector.

scholarly journals Updated search for $$ {B}_c^{+} $$ decays to two charm mesons

2021 ◽  
Vol 2021 (12) ◽  
Author(s):  
◽  
R. Aaij ◽  
A. S. W. Abdelmotteleb ◽  
C. Abellán Beteta ◽  
T. Ackernley ◽  
...  
Keyword(s):  
Branching Fractions ◽  
Final States ◽  
Charm Mesons ◽  
Data Set ◽  
Proton Proton ◽  
Neutral Pions ◽  
Proton Collisions ◽  
Decay Modes ◽  
Upper Limits ◽  
Proton Proton Collisions

Abstract A data set corresponding to an integrated luminosity of 9 fb−1 of proton-proton collisions collected by the LHCb experiment has been analysed to search for $$ {B}_c^{+}\to {D}_{(s)}^{\left(\ast \right)+}{\genfrac{}{}{0pt}{}{\left(\hbox{---} \right)}{D}}^{\left(\ast \right)0} $$ B c + → D s ∗ + — D ∗ 0 decays. The decays are fully or partially reconstructed, where one or two missing neutral pions or photons from the decay of an excited charm meson are allowed. Upper limits for the branching fractions, normalised to B+ decays to final states with similar topologies, are obtained for sixteen $$ {B}_c^{+} $$ B c + decay modes. For the decay $$ {B}_c^{+}\to {D}_s^{+}{\overline{D}}^0 $$ B c + → D s + D ¯ 0 , an excess with a significance of 3.4 standard deviations is found.

scholarly journals Search for new physics in top quark production in dilepton final states in proton-proton collisions at $$\sqrt{s} = 13\,\text {TeV} $$

2019 ◽  
Vol 79 (11) ◽  
Author(s):  
A. M. Sirunyan ◽  
◽  
A. Tumasyan ◽  
W. Adam ◽  
F. Ambrogi ◽  
...  
Keyword(s):  
Top Quark ◽  
New Physics ◽  
Effective Field ◽  
Final State ◽  
Data Set ◽  
Proton Proton ◽  
Proton Collisions ◽  
Top Quark Production ◽  
Quark Production ◽  
Proton Proton Collisions

Abstract A search for new physics in top quark production is performed in proton-proton collisions at $$13\,\text {TeV} $$13TeV. The data set corresponds to an integrated luminosity of $$35.9{\,\text {fb}^{-1}} $$35.9fb-1 collected in 2016 with the CMS detector. Events with two opposite-sign isolated leptons (electrons or muons), and $$\mathrm{b}$$b quark jets in the final state are selected. The search is sensitive to new physics in top quark pair production and in single top quark production in association with a $$\mathrm{W}$$W boson. No significant deviation from the standard model expectation is observed. Results are interpreted in the framework of effective field theory and constraints on the relevant effective couplings are set, one at a time, using a dedicated multivariate analysis. This analysis differs from previous searches for new physics in the top quark sector by explicitly separating $$\mathrm{t}\mathrm{W}$$tW from $$\mathrm{t}{\bar{\mathrm{t}}}$$tt¯ events and exploiting the specific sensitivity of the $$\mathrm{t}\mathrm{W}$$tW process to new physics.

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