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1. Search for high-mass exclusive diphoton production with tagged protons in proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$

   https://doi.org/10.1103/PhysRevD.110.012010  

   Tumasyan, A; Adam, W; Andrejkovic, J W; Bergauer, T; Chatterjee, S; Damanakis, K; Dragicevic, M; Escalante_Del_Valle, A; Hussain, P S; Jeitler, M; et al (July 2024, Physical Review D)

   A search is presented for high-mass exclusive diphoton production via photon-photon fusion in proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$ in events where both protons survive the interaction. The analysis utilizes data corresponding to an integrated luminosity of $103{\mathrm{fb}}^{-1}$ collected in 2016–2018 with the central CMS detector and the CMS and TOTEM precision proton spectrometer (PPS). Events that have two photons with high transverse momenta ( $p_{\mathrm{T}}^{\gamma }>100\mathrm{GeV}$ ), back-to-back in azimuth, and with a large diphoton invariant mass ( $m_{\gamma \gamma }>350\mathrm{GeV}$ ) are selected. To remove the dominant inclusive diphoton backgrounds, the kinematic properties of the protons detected in PPS are required to match those of the central diphoton system. Only events having opposite-side forward protons detected with a fractional momentum loss between 0.035 and 0.15 (0.18) for the detectors on the negative (positive) side of CMS are considered. One exclusive diphoton candidate is observed for an expected background of 1.1 events. Limits at 95% confidence level are derived for the four-photon anomalous coupling parameters $\left|{\zeta }_1\right|<0.073{\mathrm{TeV}}^{-4}$ and $\left|{\zeta }_2\right|<0.15{\mathrm{TeV}}^{-4}$ , using an effective field theory. Additionally, upper limits are placed on the production of axionlike particles with coupling strength to photons $f^{-1}$ that varies from $0.03{\mathrm{TeV}}^{-1}$ to $1{\mathrm{TeV}}^{-1}$ over the mass range from 500 to 2000 GeV. © 2024 CERN, for the CMS and TOTEMs Collaboration2024CERN 

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2. Search for New Resonances Decaying to Pairs of Merged Diphotons in Proton-Proton Collisions at $\sqrt{s}=13\mathrm{TeV}$

   https://doi.org/10.1103/PhysRevLett.134.041801  

   Hayrapetyan, A; Tumasyan, A; Adam, W; Andrejkovic, J W; Bergauer, T; Chatterjee, S; Damanakis, K; Dragicevic, M; Hussain, P S; Jeitler, M; et al (January 2025, Physical Review Letters)

   A search is presented for an extended Higgs sector with two new particles, $X$ and $\varphi$ , in the process $X\to \varphi \varphi \to \left(\gamma \gamma \right)\left(\gamma \gamma \right)$ . Novel neural networks classify events with diphotons that are merged and determine the diphoton masses. The search uses LHC proton-proton collision data at $\sqrt{s}=13\mathrm{TeV}$ collected with the CMS detector, corresponding to an integrated luminosity of $138{\mathrm{fb}}^{-1}$ . No evidence of such resonances is seen. Upper limits are set on the production cross section for $m_X$ between 300 and 3000 GeV and $m_{\varphi }/m_X$ between 0.5% and 2.5%, representing the most sensitive search in this channel. © 2025 CERN, for the CMS Collaboration2025CERN 

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3. Observation of Medium-Induced Yield Enhancement and Acoplanarity Broadening of Low- $p_{\mathrm{T}}$ Jets from Measurements in $pp$ and Central Pb-Pb Collisions at $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$

   https://doi.org/10.1103/PhysRevLett.133.022301  

   Acharya, S; Adamová, D; Aglieri_Rinella, G; Agnello, M; Agrawal, N; Ahammed, Z; Ahmad, S; Ahn, S U; Ahuja, I; Akindinov, A; et al (July 2024, Physical Review Letters)

   The ALICE Collaboration reports the measurement of semi-inclusive distributions of charged-particle jets recoiling from a high transverse momentum (high $p_{\mathrm{T}}$ ) hadron trigger in proton-proton and central Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$ . A data-driven statistical method is used to mitigate the large uncorrelated background in central Pb-Pb collisions. Recoil jet distributions are reported for jet resolution parameter $R=0.2$ , 0.4, and 0.5 in the range $7<p_{\mathrm{T},\text{jet}}<140\mathrm{GeV}/c$ and trigger-recoil jet azimuthal separation $\pi /2<\mathrm{\Delta }\phi <\pi$ . The measurements exhibit a marked medium-induced jet yield enhancement at low $p_{\mathrm{T}}$ and at large azimuthal deviation from $\mathrm{\Delta }\phi \sim \pi$ . The enhancement is characterized by its dependence on $\mathrm{\Delta }\phi$ , which has a slope that differs from zero by $4.7\sigma$ . Comparisons to model calculations incorporating different formulations of jet quenching are reported. These comparisons indicate that the observed yield enhancement arises from the response of the QGP medium to jet propagation. © 2024 CERN, for the ALICE Collaboration2024CERN 

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4. Search for heavy neutral resonances decaying to tau lepton pairs in proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$

   https://doi.org/10.1103/PhysRevD.111.112004  

   Hayrapetyan, A; Tumasyan, A; Adam, W; Andrejkovic, J W; Benato, L; Bergauer, T; Chatterjee, S; Damanakis, K; Dragicevic, M; Hussain, P S; et al (June 2025, Physical Review D)

   PRD (Ed.)

   A search for heavy neutral gauge bosons ( $Z^{\prime }$ ) decaying into a pair of tau leptons is performed in proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$ at the CERN LHC. The data were collected with the CMS detector and correspond to an integrated luminosity of $138{\mathrm{fb}}^{-1}$ . The observations are found to be in agreement with the expectation from standard model processes. Limits at 95% confidence level are set on the product of the $Z^{\prime }$ production cross section and its branching fraction to tau lepton pairs for a range of $Z^{\prime }$ boson masses. For a narrow resonance in the sequential standard model scenario, a $Z^{\prime }$ boson with a mass below 3.5 TeV is excluded. This is the most stringent limit to date from this type of search. © 2025 CERN, for the CMS Collaboration2025CERN 

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5. Observation of Enhanced Long-Range Elliptic Anisotropies Inside High-Multiplicity Jets in $pp$ Collisions at $\sqrt{s}=13\mathrm{TeV}$

   https://doi.org/10.1103/PhysRevLett.133.142301  

   Hayrapetyan, A; Tumasyan, A; Adam, W; Andrejkovic, J W; Bergauer, T; Chatterjee, S; Damanakis, K; Dragicevic, M; Hussain, P S; Jeitler, M; et al (September 2024, Physical Review Letters)

   A search for collective effects inside jets produced in proton-proton collisions is performed via correlation measurements of charged particles using the CMS detector at the CERN LHC. The analysis uses data collected at a center-of-mass energy of $\sqrt{s}=13\mathrm{TeV}$ , corresponding to an integrated luminosity of $138{\mathrm{fb}}^{-1}$ . Jets are reconstructed with the anti- $k_{\mathrm{T}}$ algorithm with a distance parameter of 0.8 and are required to have transverse momentum greater than 550 GeV and pseudorapidity $\left|{\eta }^{\text{jet}}\right|<1.6$ . Two-particle correlations among the charged particles within the jets are studied as functions of the particles’ azimuthal angle and pseudorapidity separations ( $\mathrm{\Delta }{\varphi }^{*}$ and $\mathrm{\Delta }{\eta }^{*}$ ) in a jet coordinate basis, where particles’ ${\eta }^{*}$ , ${\varphi }^{*}$ are defined relative to the direction of the jet. The correlation functions are studied in classes of in-jet charged-particle multiplicity up to $N_{\mathrm{ch}}^{\mathrm{j}}\approx 100$ . Fourier harmonics are extracted from long-range azimuthal correlation functions to characterize azimuthal anisotropy for $\left|\mathrm{\Delta }{\eta }^{*}\right|>2$ . For low- $N_{\mathrm{ch}}^{\mathrm{j}}$ jets, the long-range elliptic anisotropic harmonic, $v_2^{*}$ , is observed to decrease with $N_{\mathrm{ch}}^{\mathrm{j}}$ . This trend is well described by Monte Carlo event generators. However, a rising trend for $v_2^{*}$ emerges at $N_{\mathrm{ch}}^{\mathrm{j}}\gtrsim 80$ , hinting at a possible onset of collective behavior, which is not reproduced by the models tested. This observation yields new insights into the dynamics of jet evolution in the vacuum. © 2024 CERN, for the CMS Collaboration2024CERN 

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