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1. The LHC as a Neutrino-Ion Collider

   https://doi.org/10.1140/epjc/s10052-024-12665-1  

   Cruz-Martinez, Juan M; Fieg, Max; Giani, Tommaso; Krack, Peter; Mäkelä, Toni; Rabemananjara, Tanjona R; Rojo, Juan (April 2024, The European Physical Journal C)

   Abstract Proton-proton collisions at the LHC generate a high-intensity collimated beam of neutrinos in the forward (beam) direction, characterised by energies of up to several TeV. The recent observation of LHC neutrinos by FASER$$\nu $$ $\nu$and SND@LHC signifies that this previously overlooked particle beam is now available for scientific investigation. Here we quantify the impact that neutrino deep-inelastic scattering (DIS) measurements at the LHC would have on the parton distributions (PDFs) of protons and heavy nuclei. We generate projections for DIS structure functions for FASER$$\nu $$ $\nu$and SND@LHC at Run III, as well as for the FASER$$\nu $$ $\nu$2, AdvSND, and FLArE experiments to be hosted at the proposed Forward Physics Facility (FPF) operating concurrently with the High-Luminosity LHC (HL-LHC). We determine that up to one million electron-neutrino and muon-neutrino DIS interactions within detector acceptance can be expected by the end of the HL-LHC, covering a kinematic region inxand$$Q^2$$ $Q^2$overlapping with that of the Electron-Ion Collider. Including these DIS projections in global (n)PDF analyses, specifically PDF4LHC21, NNPDF4.0, and EPPS21, reveals a significant reduction in PDF uncertainties, in particular for strangeness and the up and down valence PDFs. We show that LHC neutrino data enable improved theoretical predictions for core processes at the HL-LHC, such as Higgs and weak gauge boson production. Our analysis demonstrates that exploiting the LHC neutrino beam effectively provides CERN with a “Neutrino-Ion Collider” without requiring modifications in its accelerator infrastructure. 

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2. Susy at the FPF

   https://doi.org/10.1140/epjc/s10052-025-13839-1  

   Anchordoqui, Luis A; Antoniadis, Ignatios; Benakli, Karim; Cunat, Jules; Lüst, Dieter (February 2025, The European Physical Journal C)

   Abstract Experimental searches for supersymmetry (SUSY) are entering a new era. The failure to observe signals of sparticle production at the large hadron collider (LHC) has eroded the central motivation for SUSY breaking at the weak scale. However, String Theory requires SUSY at the fundamental scale$$M_s$$ $M_s$and hence SUSY could be broken at some high scale below$$M_s$$ $M_s$. Actually, if this were the case, the lack of experimental evidence for low-energy SUSY could have been anticipated, because most stringy models with high-scale SUSY breaking predict that sparticles would start popping up above about 10 TeV, well beyond the reach of current LHC experiments. We show that using next generation LHC experiments currently envisioned for the Forward Physics Facility (FPF) we could search for signals of neutrino-modulino oscillations to probe models with string scale in the grand unification region and SUSY breaking driven by sequestered gravity in gauge mediation. This is possible because of the unprecedented flux of neutrinos to be produced as secondary products in LHC collisions during the high-luminosity era and the capability of FPF experiments to detect and identify their flavors. 

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3. Electrically tunable total reflection of light by oblique helicoidal cholesteric

   https://doi.org/10.1557/s43577-024-00723-8  

   Iadlovska, Olena S; Thapa, Kamal; Rajabi, Mojtaba; Mrukiewicz, Mateusz; Shiyanovskii, Sergij V; Lavrentovich, Oleg D (June 2024, MRS Bulletin)

   AbstractAn oblique helicoidal state of a cholesteric liquid crystal (Ch_OH) is capable of continuous change of the pitch$$P$$ $P$in response to an applied electric field. Such a structure reflects 50% of the unpolarized light incident along the Ch_OHaxis in the electrically tunable band determined by$$P$$ $P$/2. Here, we demonstrate that at an oblique incidence of light, Ch_OHreflects 100% of light of any polarization. This singlet band of total reflection is associated with the full pitch$$P$$ $P$. We also describe the satellite$$P/2$$ $P/2$,$$P/3$$ $P/3$, and$$P/4$$ $P/4$bands. The$$P/2$$ $P/2$and$$P/4$$ $P/4$bands are triplets, whereas$$P/3$$ $P/3$band is a singlet caused by multiple scatterings at$$P$$ $P$and$$P/2$$ $P/2$. A single Ch_OHcell acted upon by an electric field tunes all these bands in a very broad spectral range, from ultraviolet to infrared and beyond, thus representing a structural color device with enormous potential for optical and photonic applications. Impact statementPigments, inks, and dyes produce colors by partially consuming the energy of light. In contrast, structural colors caused by interference and diffraction of light scattered at submicrometer length scales do not involve energy losses, which explains their widespread in Nature and the interest of researchers to develop mimicking materials. The grand challenge is to produce materials in which the structural colors could be dynamically tuned. Among the oldest known materials producing structural colors are cholesteric liquid crystals. Light causes coloration by selective Bragg reflection at the periodic helicoidal structure formed by cholesteric molecules. The cholesteric pitch and thus the color can be altered by chemical composition or by temperature, but, unfortunately, dynamic tuning by electromagnetic field has been elusive. Here, we demonstrate that a cholesteric material in a new oblique helicoidal Ch_OHstate could produce total reflection of an obliquely incident light of any polarization. The material reflects 100% of light within a band that is continuously tunable by the electric field through the entire visible spectrum while preserving its maximum efficiency. Broad electric tunability of total reflection makes the Ch_OHmaterial suitable for applications in energy-saving smart windows, transparent displays, communications, lasers, multispectral imaging, and virtual and augmented reality. Graphical Abstract 

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4. FPF@FCC: neutrino, QCD, and BSM physics opportunities with far-forward experiments at a 100 TeV Proton Collider

   https://doi.org/10.1007/JHEP01(2025)094  

   Mammen_Abraham, Roshan; Adhikary, Jyotismita; Feng, Jonathan L; Fieg, Max; Kling, Felix; Li, Jinmian; Pei, Junle; Rabemananjara, Tanjona R; Rojo, Juan; Trojanowski, Sebastian (January 2025, Journal of High Energy Physics)

   A<sc>bstract</sc> Proton-proton collisions at energy-frontier facilities produce an intense flux of high-energy light particles, including neutrinos, in the forward direction. At the LHC, these particles are currently being studied with the far-forward experiments FASER/FASERνand SND@LHC, while new dedicated experiments have been proposed in the context of a Forward Physics Facility (FPF) operating at the HL-LHC. Here we present a first quantitative exploration of the reach for neutrino, QCD, and BSM physics of far-forward experiments integrated within the proposed Future Circular Collider (FCC) project as part of its proton-proton collision program (FCC-hh) at$$ \sqrt{s} $$ $\sqrt{s}$≃ 100 TeV. We find that 10⁹electron/muon neutrinos and 10⁷tau neutrinos could be detected, an increase of several orders of magnitude compared to (HL-)LHC yields. We study the impact of neutrino DIS measurements at the FPF@FCC to constrain the unpolarised and spin partonic structure of the nucleon and assess their sensitivity to nuclear dynamics down tox∼ 10⁻⁹with neutrinos produced in proton-lead collisions. We demonstrate that the FPF@FCC could measure the neutrino charge radius forν_eandν_μand reach down to five times the SM value forν_τ. We fingerprint the BSM sensitivity of the FPF@FCC for a variety of models, including dark Higgs bosons, relaxion-type scenarios, quirks, and millicharged particles, finding that these experiments would be able to discover LLPs with masses as large as 50 GeV and couplings as small as 10⁻⁸, and quirks with masses up to 10 TeV. Our study highlights the remarkable opportunities made possible by integrating far-forward experiments into the FCC project, and it provides new motivation for the FPF at the HL-LHC as an essential precedent to optimize the forward physics experiments that will enable the FCC to achieve its full physics potential. 

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5. Investigating $D^0$ meson production in p-Pb collisions at 5.02 TeV with a multi-phase transport model

   https://doi.org/10.1140/epjc/s10052-024-13265-9  

   Zhang, Chao; Zheng, Liang; Shi, Shusu; Lin, Zi-Wei (September 2024, The European Physical Journal C)

   Abstract We study the production of$$D^0$$ $D^0$meson inp+pandp-Pb collisions using the improved AMPT model considering both coalescence and independent fragmentation of charm quarks after the Cronin broadening is included. After a detailed discussion of the improvements implemented in the AMPT model for heavy quark production, we show that the modified AMPT model can provide a good description of$$D^0$$ $D^0$meson spectra inp-Pb collisions, the$$Q_{\textrm{pPb}}$$ $Q_{\text{pPb}}$data at different centralities and$$R_{\textrm{pPb}}$$ $R_{\text{pPb}}$data in both mid- and forward (backward) rapidities. We also studied the effects of nuclear shadowing and parton cascade on the rapidity dependence of$$D^{0}$$ $D^0$meson production and$$R_{\textrm{pPb}}$$ $R_{\text{pPb}}$. Our results indicate that using the same strength of the Cronin effect (i.e$$\delta $$ $\delta$value) as that obtained from the mid-rapidity data leads to a considerable overestimation of the$$D^0$$ $D^0$meson spectra and$$R_{\textrm{pPb}}$$ $R_{\text{pPb}}$data at high$$p_{\textrm{T}}$$ $p_{\text{T}}$in the backward rapidity. As a result, the$$\delta $$ $\delta$is determined via a$$\chi ^2$$ ${\chi }^2$fitting of the$$R_{\textrm{pPb}}$$ $R_{\text{pPb}}$data across various rapidities. This work lays the foundation for a better understanding of cold-nuclear-matter (CNM) effects in relativistic heavy-ion collisions. 

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