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Title: $$K^{+}\Lambda $$ photoproduction at forward angles and low momentum transfer

Abstract $$\gamma p \rightarrow K^{+} \Lambda $$ γ p → K + Λ differential cross sections and recoil polarisation data from threshold for extremely forward angles are presented. The measurements were performed at the BGOOD experiment at ELSA, utilising the high angular and momentum resolution forward spectrometer for charged particle identification. The high statistics and forward angle acceptance enables the extraction of the cross section as the minimum momentum transfer to the recoiling hyperon is approached.

Jude, Thomas; Alef, Stefan; Bauer, Patrick; Beck, Reinhard; Braghieri, Alessandro; Cole, Philip; Di Salvo, Rachele; Elsner, Daniel; Fantini, Alessia; Freyermuth, Oliver; et al(
, EPJ Web of Conferences)

Beck, R.; Thiel, A.; Thoma, U.; Wunderlich, Y.
(Ed.)

The BGO-OD experiment at the ELSA accelerator facility uses an energy tagged bremsstrahlung photon beam to investigate the excitation structure of the nucleon. The setup consists of a highly segmented BGO calorimeter surrounding the target, with a particle tracking magnetic spectrometer at forward angles. BGO-OD is ideal for investigating low momentum transfer processes due to the acceptance and high momentum resolution at forward angles. In particular, this enables the investigation of strangeness photoproduction where t-channel exchange mechanisms play an important role. This also allows access to low momentum exchange kinematics where extended, molecular structure may manifest in reaction mechanisms. Firstmore »key results at low t indicate a cusp-like structure in K + Σ 0 photoproduction at W = 1900 MeV, line shapes and differential cross sections for K + Λ(1405)→ K + Σ 0 π 0 , and a peak structure in K 0 S Σ 0 photoproduction. The peak in the K 0 S Σ 0 channel appears consistent with meson-baryon generated states, where equivalent models have been used to describe the P C pentaquark candidates in the heavy charmed quark sector.« less

Adam, J.; Adamczyk, L.; Adams, J. R.; Adkins, J. K.; Agakishiev, G.; Aggarwal, M. M.; Ahammed, Z.; Alekseev, I.; Anderson, D. M.; Aparin, A.; et al(
, Journal of High Energy Physics)

A bstract We report on the measurement of the Central Exclusive Production of charged particle pairs h + h − ( h = π, K, p ) with the STAR detector at RHIC in proton-proton collisions at $$ \sqrt{s} $$ s = 200 GeV. The charged particle pairs produced in the reaction pp → p ′ + h + h − + p ′ are reconstructed from the tracks in the central detector and identified using the specific energy loss and the time of flight method, while the forward-scattered protons are measured in the Roman Pot system. Exclusivity of themore »event is guaranteed by requiring the transverse momentum balance of all four final-state particles. Differential cross sections are measured as functions of observables related to the central hadronic final state and to the forward-scattered protons. They are measured in a fiducial region corresponding to the acceptance of the STAR detector and determined by the central particles’ transverse momenta and pseudorapidities as well as by the forward-scattered protons’ momenta. This fiducial region roughly corresponds to the square of the four-momentum transfers at the proton vertices in the range 0 . 04 GeV 2 < −t 1 , −t 2 < 0 . 2 GeV 2 , invariant masses of the charged particle pairs up to a few GeV and pseudorapidities of the centrally-produced hadrons in the range |η| < 0 . 7. The measured cross sections are compared to phenomenological predictions based on the Double Pomeron Exchange (DPE) model. Structures observed in the mass spectra of π + π − and K + K − pairs are consistent with the DPE model, while angular distributions of pions suggest a dominant spin-0 contribution to π + π − production. For π + π − production, the fiducial cross section is extrapolated to the Lorentz-invariant region, which allows decomposition of the invariant mass spectrum into continuum and resonant contributions. The extrapolated cross section is well described by the continuum production and at least three resonances, the f 0 (980), f 2 (1270) and f 0 (1500), with a possible small contribution from the f 0 (1370). Fits to the extrapolated differential cross section as a function of t 1 and t 2 enable extraction of the exponential slope parameters in several bins of the invariant mass of π + π − pairs. These parameters are sensitive to the size of the interaction region.« less

Acharya, S.; Adamová, D.; Adler, A.; Adolfsson, J.; Aglieri Rinella, G.; Agnello, M.; Agrawal, N.; Ahammed, Z.; Ahmad, S.; Ahn, S. U.; et al(
, The European Physical Journal C)

Abstract The multiplicity dependence of jet production in pp collisions at the centre-of-mass energy of $$\sqrt{s} = 13\ {\mathrm {TeV}}$$ s = 13 TeV is studied for the first time. Jets are reconstructed from charged particles using the anti- $$k_\mathrm {T}$$ k T algorithm with resolution parameters R varying from 0.2 to 0.7. The jets are measured in the pseudorapidity range $$|\eta _{\mathrm{jet}}|< 0.9-R$$ | η jet | < 0.9 - R and in the transverse momentum range $$5more »by the ALICE forward detector V0. The $$p_{\mathrm T}$$ p T differential cross section of charged-particle jets are compared to leading order (LO) and next-to-leading order (NLO) perturbative quantum chromodynamics (pQCD) calculations. It is found that the data are better described by the NLO calculation, although the NLO prediction overestimates the jet cross section below $$20\ {\mathrm {GeV}}/c$$ 20 GeV / c . The cross section ratios for different R are also measured and compared to model calculations. These measurements provide insights into the angular dependence of jet fragmentation. The jet yield increases with increasing self-normalised charged-particle multiplicity. This increase shows only a weak dependence on jet transverse momentum and resolution parameter at the highest multiplicity. While such behaviour is qualitatively described by the present version of PYTHIA, quantitative description may require implementing new mechanisms for multi-particle production in hadronic collisions.« less

Acharya, S.; Adamová, D.; Adler, A.; Adolfsson, J.; Aggarwal, M. M.; Rinella, G. Aglieri; Agnello, M.; Agrawal, N.; Ahammed, Z.; Ahmad, S.; et al(
, The European Physical Journal C)

Abstract The production of $$\pi ^{\pm }$$ π ± , $$\mathrm{K}^{\pm }$$ K ± , $$\mathrm{K}^{0}_{S}$$ K S 0 , $$\mathrm{K}^{*}(892)^{0}$$ K ∗ ( 892 ) 0 , $$\mathrm{p}$$ p , $$\phi (1020)$$ ϕ ( 1020 ) , $$\Lambda $$ Λ , $$\Xi ^{-}$$ Ξ - , $$\Omega ^{-}$$ Ω - , and their antiparticles was measured in inelastic proton–proton (pp) collisions at a center-of-mass energy of $$\sqrt{s}$$ s = 13 TeV at midrapidity ( $$|y|<0.5$$ | y | < 0.5 ) as a function of transverse momentum ( $$p_{\mathrm{T}}$$ p T ) using the ALICE detector at the CERNmore »LHC. Furthermore, the single-particle $$p_{\mathrm{T}}$$ p T distributions of $$\mathrm{K}^{0}_{S}$$ K S 0 , $$\Lambda $$ Λ , and $$\overline{\Lambda }$$ Λ ¯ in inelastic pp collisions at $$\sqrt{s} = 7$$ s = 7 TeV are reported here for the first time. The $$p_{\mathrm{T}}$$ p T distributions are studied at midrapidity within the transverse momentum range $$0\le p_{\mathrm{T}}\le 20$$ 0 ≤ p T ≤ 20 GeV/ c , depending on the particle species. The $$p_{\mathrm{T}}$$ p T spectra, integrated yields, and particle yield ratios are discussed as a function of collision energy and compared with measurements at lower $$\sqrt{s}$$ s and with results from various general-purpose QCD-inspired Monte Carlo models. A hardening of the spectra at high $$p_{\mathrm{T}}$$ p T with increasing collision energy is observed, which is similar for all particle species under study. The transverse mass and $$x_{\mathrm{T}}\equiv 2p_{\mathrm{T}}/\sqrt{s}$$ x T ≡ 2 p T / s scaling properties of hadron production are also studied. As the collision energy increases from $$\sqrt{s}$$ s = 7–13 TeV, the yields of non- and single-strange hadrons normalized to the pion yields remain approximately constant as a function of $$\sqrt{s}$$ s , while ratios for multi-strange hadrons indicate enhancements. The $$p_\mathrm{{T}}$$ p T -differential cross sections of $$\pi ^{\pm }$$ π ± , $$\mathrm {K}^{\pm }$$ K ± and $$\mathrm {p}$$ p ( $$\overline{\mathrm{p}}$$ p ¯ ) are compared with next-to-leading order perturbative QCD calculations, which are found to overestimate the cross sections for $$\pi ^{\pm }$$ π ± and $$\mathrm{p}$$ p ( $$\overline{\mathrm{p}}$$ p ¯ ) at high $$p_\mathrm{{T}}$$ p T .« less

Cirigliano, Vincenzo; Dekens, Wouter; de Vries, Jordy; Hoferichter, Martin; Mereghetti, Emanuele(
, Journal of High Energy Physics)

A bstract We present a method to determine the leading-order (LO) contact term contributing to the nn → ppe − e − amplitude through the exchange of light Majorana neutrinos. Our approach is based on the representation of the amplitude as the momentum integral of a known kernel (proportional to the neutrino propagator) times the generalized forward Compton scattering amplitude n ( p 1 ) n ( p 2 ) W + ( k ) → $$ p\left({p}_1^{\prime}\right)p\left({p}_2^{\prime}\right){W}^{-}(k) $$ p p 1 ′ p p 2 ′ W − k , in analogy to the Cottingham formula for the electromagneticmore »contribution to hadron masses. We construct model-independent representations of the integrand in the low- and high-momentum regions, through chiral EFT and the operator product expansion, respectively. We then construct a model for the full amplitude by interpolating between these two regions, using appropriate nucleon factors for the weak currents and information on nucleon-nucleon ( NN ) scattering in the 1 S 0 channel away from threshold. By matching the amplitude obtained in this way to the LO chiral EFT amplitude we obtain the relevant LO contact term and discuss various sources of uncertainty. We validate the approach by computing the analog I = 2 NN contact term and by reproducing, within uncertainties, the charge-independence-breaking contribution to the 1 S 0 NN scattering lengths. While our analysis is performed in the $$ \overline{\mathrm{MS}} $$ MS ¯ scheme, we express our final result in terms of the scheme-independent renormalized amplitude $$ {\mathcal{A}}_{\nu}\left(\left|\mathbf{p}\right|,\left|\mathbf{p}^{\prime}\right|\right) $$ A ν p p ′ at a set of kinematic points near threshold. We illustrate for two cutoff schemes how, using our synthetic data for $$ {\mathcal{A}}_{\nu } $$ A ν , one can determine the contact-term contribution in any regularization scheme, in particular the ones employed in nuclear-structure calculations for isotopes of experimental interest.« less

Alef, S., Bauer, P., Bayadilov, D., Beck, R., Bella, A., Bieling, J., Braghieri, A., Cole, P. L., Elsner, D., Di Salvo, R., Fantini, A., Freyermuth, O., Frommberger, F., Ghio, F., Goertz, S., Gridnev, A., Hammann, D., Hannappel, J., Jude, T. C., Kohl, K., Kozlenko, N., Lapik, A., Levi Sandri, P., Lisin, V., Mandaglio, G., Messi, F., Messi, R., Moricciani, D., Nedorezov, V., Nikonov, V. A., Novinskiy, D., Pedroni, P., Polonskiy, A., Reitz, B.-E., Romaniuk, M., Sarantsev, A. V., Scheluchin, G., Schmieden, H., Stuglev, A., Sumachev, V., Vegna, V., Tarakanov, V., and Zimmermann, T. $$K^{+}\Lambda $$ photoproduction at forward angles and low momentum transfer. Retrieved from https://par.nsf.gov/biblio/10283822. The European Physical Journal A 57.2 Web. doi:10.1140/epja/s10050-021-00392-0.

Alef, S., Bauer, P., Bayadilov, D., Beck, R., Bella, A., Bieling, J., Braghieri, A., Cole, P. L., Elsner, D., Di Salvo, R., Fantini, A., Freyermuth, O., Frommberger, F., Ghio, F., Goertz, S., Gridnev, A., Hammann, D., Hannappel, J., Jude, T. C., Kohl, K., Kozlenko, N., Lapik, A., Levi Sandri, P., Lisin, V., Mandaglio, G., Messi, F., Messi, R., Moricciani, D., Nedorezov, V., Nikonov, V. A., Novinskiy, D., Pedroni, P., Polonskiy, A., Reitz, B.-E., Romaniuk, M., Sarantsev, A. V., Scheluchin, G., Schmieden, H., Stuglev, A., Sumachev, V., Vegna, V., Tarakanov, V., & Zimmermann, T. $$K^{+}\Lambda $$ photoproduction at forward angles and low momentum transfer. The European Physical Journal A, 57 (2). Retrieved from https://par.nsf.gov/biblio/10283822. https://doi.org/10.1140/epja/s10050-021-00392-0

Alef, S., Bauer, P., Bayadilov, D., Beck, R., Bella, A., Bieling, J., Braghieri, A., Cole, P. L., Elsner, D., Di Salvo, R., Fantini, A., Freyermuth, O., Frommberger, F., Ghio, F., Goertz, S., Gridnev, A., Hammann, D., Hannappel, J., Jude, T. C., Kohl, K., Kozlenko, N., Lapik, A., Levi Sandri, P., Lisin, V., Mandaglio, G., Messi, F., Messi, R., Moricciani, D., Nedorezov, V., Nikonov, V. A., Novinskiy, D., Pedroni, P., Polonskiy, A., Reitz, B.-E., Romaniuk, M., Sarantsev, A. V., Scheluchin, G., Schmieden, H., Stuglev, A., Sumachev, V., Vegna, V., Tarakanov, V., and Zimmermann, T.
"$$K^{+}\Lambda $$ photoproduction at forward angles and low momentum transfer". The European Physical Journal A 57 (2). Country unknown/Code not available. https://doi.org/10.1140/epja/s10050-021-00392-0.https://par.nsf.gov/biblio/10283822.

@article{osti_10283822,
place = {Country unknown/Code not available},
title = {$$K^{+}\Lambda $$ photoproduction at forward angles and low momentum transfer},
url = {https://par.nsf.gov/biblio/10283822},
DOI = {10.1140/epja/s10050-021-00392-0},
abstractNote = {Abstract $$\gamma p \rightarrow K^{+} \Lambda $$ γ p → K + Λ differential cross sections and recoil polarisation data from threshold for extremely forward angles are presented. The measurements were performed at the BGOOD experiment at ELSA, utilising the high angular and momentum resolution forward spectrometer for charged particle identification. The high statistics and forward angle acceptance enables the extraction of the cross section as the minimum momentum transfer to the recoiling hyperon is approached.},
journal = {The European Physical Journal A},
volume = {57},
number = {2},
author = {Alef, S. and Bauer, P. and Bayadilov, D. and Beck, R. and Bella, A. and Bieling, J. and Braghieri, A. and Cole, P. L. and Elsner, D. and Di Salvo, R. and Fantini, A. and Freyermuth, O. and Frommberger, F. and Ghio, F. and Goertz, S. and Gridnev, A. and Hammann, D. and Hannappel, J. and Jude, T. C. and Kohl, K. and Kozlenko, N. and Lapik, A. and Levi Sandri, P. and Lisin, V. and Mandaglio, G. and Messi, F. and Messi, R. and Moricciani, D. and Nedorezov, V. and Nikonov, V. A. and Novinskiy, D. and Pedroni, P. and Polonskiy, A. and Reitz, B.-E. and Romaniuk, M. and Sarantsev, A. V. and Scheluchin, G. and Schmieden, H. and Stuglev, A. and Sumachev, V. and Vegna, V. and Tarakanov, V. and Zimmermann, T.},
}