First Results in the Search for Dark Sectors at NA64 with the CERN SPS High Energy Muon Beam.

We report the first search for dark sectors performed at the NA64 experiment employing a high energy muon beam and a missing energy-momentum technique. Muons from the M2 beamline at the CERN Super Proton Synchrotron with a momentum of 160 GeV/c are directed to an active target. The signal signature consists of a single scattered muon with momentum <80 GeV/c in the final state, accompanied by missing energy, i.e., no detectable activity in the downstream calorimeters. For a total dataset of (1.98±0.02)×10^{10} muons on target, no event is observed in the expected signal region. This allows us to set new limits on the remaining (m_{Z^{'}},g_{Z^{'}}) parameter space of a new Z^{'} (L_{µ}-L_{τ}) vector boson which could explain the muon (g-2)_{µ} anomaly. Additionally, our study excludes part of the parameter space suggested by the thermal dark matter relic abundance. Our results pave the way to explore dark sectors and light dark matter with muon beams in a unique and complementary way to other experiments.

Search for Light Dark Matter with NA64 at CERN.

Thermal dark matter models with particle χ masses below the electroweak scale can provide an explanation for the observed relic dark matter density. This would imply the existence of a new feeble interaction between the dark and ordinary matter. We report on a new search for the sub-GeV χ production through the interaction mediated by a new vector boson, called the dark photon A^{'}, in collisions of 100 GeV electrons with the active target of the NA64 experiment at the CERN SPS. With 9.37×10^{11} electrons on target collected during 2016-2022 runs NA64 probes for the first time the well-motivated region of parameter space of benchmark thermal scalar and fermionic dark matter models. No evidence for dark matter production has been found. This allows us to set the most sensitive limits on the A^{'} couplings to photons for masses m_{A^{'}}≲0.35 GeV, and to exclude scalar and Majorana dark matter with the χ-A^{'} coupling α_{D}≤0.1 for masses 0.001≲m_{χ}≲0.1 GeV and 3m_{χ}≤m_{A^{'}}.

ANALYSIS THE RESULTS OF SURGICAL TREATMENT AND EARLY REHABILITATION OF PATIENTS WITH MASSIVE TEARS THE ROTATOR CUFF THE SHOULDER.

The aim of the study was to evaluate the treatment outcomes in patients who underwent arthroscopic repair of large and massive rotator cuff tears and underwent rehabilitation at different stages of the recovery process. The clinical study group consisted of 88 patients, with an age range of 47 to 68 years (mean age 52,7±9,5 years). All patients underwent a double-row repair of the rotator cuff tendons and tenodesis or tenotomy of the long head of the biceps tendon under arthroscopic guidance. The results were assessed using the Constant Shoulder Score and the Oxford Shoulder Score scales at 6 and 12 months after the surgery. A total of 88 patients were selected, with 50 patients in the main group (MG) who had a 6-week immobilization period. The control group (CG) consisted of 38 patients who had a shortened immobilization period of 3-4 weeks due to patient preference or recommendations from other rehabilitation centers where patients underwent rehabilitation. Shoulder immobilization was performed using a standard sling with a triangular pillow and a 15° abduction angle in the shoulder joint. Following the surgeon's recommendation, all patients were offered a rehabilitation program consisting of three periods: immobilization (0-6 weeks), functional (6-12 weeks), and training (>12 weeks) periods. Comparative analysis of the treatment results using the Oxford Shoulder Score scale showed that significantly better results were obtained in the MG patients (41,5±2,1 points) compared to the CG patients (34,2±3,6 points) at 6,2±1,2 months (p˂0.05). Comparative analysis of the treatment results using the Oxford Shoulder Score scale at 12,2±1,3 months showed that there were no statistically significant differences between the MG and CG results (MG - 44,5±2,2 and CG - 42,4±3, p>0,05). Similarly, according to the Constant Shoulder Score scale, better results were observed in the MG both at 6 months and 12 months after the surgery (excellent in 82% of MG vs 36.8% in CG, good in 18% of MG vs 57.9% in CG, respectively). Thus, in the short term, early activation of the operated joint leads to delayed healing of the operated tissues and worsening of joint function, as confirmed by the comparative analysis of the examined groups. Significant advantages of prolonged immobilization (at least 6 weeks) were found in short-term observation (up to 6 months), and no differences in functional outcomes were observed in the long term during the follow-up at 12 months.

THE USE OF RADIOFREQUENCY NEUROABLATION IN THE TREATMENT OF OMALGIA IN PATIENTS WITH SHOULDER JOINT ARTHROSIS.

The aim of the study was to evaluate the effectiveness of radiofrequency denervation (neuroablation) of the suprascapular nerve in the treatment process of omalgia in patients with degenerative and dystrophic disorders of the shoulder joint. 31 patients (31 joints were researched) took the treatment and analyzed their data in the rehabilitation department of the State Institution "Institute of Traumatology and Orthopedics of the National Academy of Medical Sciences of Ukraine" from 2019 to 2021. X-ray assessment was performed to find out the stage of the disease according to the classification of M. Lequesne Kellgren and J. Lawrence. All patients had radiofrequency neuroablation of the suprascapular nerve. Patients were assessed before the RFN procedure, after 1, 3, 6, and 12 months after the procedure. Due to performed treatment, the average VAS score for pain was 7,65±1,23 cm. A decrease in pain level by 3 cm or more was considered reliable. 1 month after suprascapular nerve RFN we had a significant decrease in pain syndrome according to VAS in the group of patients within 3,87±1,06 cm (p<0,05); after 3 months a stable positive remained at the 3,1±1,42 cm; after 6 months began to gradually deteriorate to 5,52±1,24 cm and remained after 12 months at the 5,2±1,58 cm. Thus, the suprascapular nerve RFN procedure allows for maintaining a stable positive result for 6 months with subsequent deterioration. After 12 months abandoned the use of NSAIDs - 29,03% of patients and continued to additionally use NSAIDs for pain relief sometimes or constantly almost 64,52% of the group examined. The results of our studies complement those of Taverner et al., Eyigor et al., indicating a trend toward a decrease in pain and functional limitations among patients with omalgia after the RFN procedure, and the preservation of the effect during the follow-up year after the procedure. The suprascapular nerve RFN procedure makes it possible to reduce the level of pain syndrome and refuse the use of painkillers in patients with shoulder joint arthrosis in almost 30-40% of cases, and the effect of pain relief lasts from 6 to 12 months in most cases.

Search for a New B-L Z

A search for a new Z^{'} gauge boson associated with (un)broken B-L symmetry in the keV-GeV mass range is carried out for the first time using the missing-energy technique in the NA64 experiment at the CERN SPS. From the analysis of the data with 3.22×10^{11} electrons on target collected during 2016-2021 runs, no signal events were found. This allows us to derive new constraints on the Z^{'}-e coupling strength, which, for the mass range 0.3≲m_{Z^{'}}≲100 MeV, are more stringent compared to those obtained from the neutrino-electron scattering data.

Results from the Baksan Experiment on Sterile Transitions (BEST).

The Baksan Experiment on Sterile Transitions (BEST) was designed to investigate the deficit of electron neutrinos ν_{e} observed in previous gallium-based radiochemical measurements with high-intensity neutrino sources, commonly referred to as the "gallium anomaly," which could be interpreted as evidence for oscillations between ν_{e} and sterile neutrino (ν_{s}) states. A 3.414-MCi ^{51}Cr ν_{e} source was placed at the center of two nested Ga volumes and measurements were made of the production of ^{71}Ge through the charged current reaction, ^{71}Ga(ν_{e},e^{-})^{71}Ge, at two average distances. The measured production rates for the inner and the outer targets, respectively, are [54.9_{-2.4}^{+2.5}(stat)±1.4(syst)] and [55.6_{-2.6}^{+2.7}(stat)±1.4(syst)] atoms of ^{71}Ge/d. The ratio (R) of the measured rate of ^{71}Ge production at each distance to the expected rate from the known cross section and experimental efficiencies are R_{in}=0.79±0.05 and R_{out}=0.77±0.05. The ratio of the outer to the inner result is 0.97±0.07, which is consistent with unity within uncertainty. The rates at each distance were found to be similar, but 20%-24% lower than expected, thus reaffirming the anomaly. These results are consistent with ν_{e}→ν_{s} oscillations with a relatively large Δm^{2} (>0.5 eV^{2}) and mixing sin^{2}2θ (≈0.4).

Probing the explanation of the muon (g-2) anomaly and thermal light dark matter with the semi-visible dark photon channel.

We report the results of a search for a new vector boson ( A ' ) decaying into two dark matter particles χ 1 χ 2 of different mass. The heavier χ 2 particle subsequently decays to χ 1 and an off-shell Dark Photon A ' ∗ → e + e - . For a sufficiently large mass splitting, this model can explain in terms of new physics the recently confirmed discrepancy observed in the muon anomalous magnetic moment at Fermilab. Remarkably, it also predicts the observed yield of thermal dark matter relic abundance. A detailed Monte-Carlo simulation was used to determine the signal yield and detection efficiency for this channel in the NA64 setup. The results were obtained re-analyzing the previous NA64 searches for an invisible decay A ' → χ χ ¯ and axion-like or pseudo-scalar particles a → γ γ . With this method, we exclude a significant portion of the parameter space justifying the muon g-2 anomaly and being compatible with the observed dark matter relic density for A ' masses from 2 m e up to 390 MeV and mixing parameter ε between 3 × 10 - 5 and 2 × 10 - 2 .

Constraints on New Physics in Electron g-2 from a Search for Invisible Decays of a Scalar, Pseudoscalar, Vector, and Axial Vector.

We performed a search for a new generic X boson, which could be a scalar (S), pseudoscalar (P), vector (V), or an axial vector (A) particle produced in the 100 GeV electron scattering off nuclei, e^{-}Z→e^{-}ZX, followed by its invisible decay in the NA64 experiment at CERN. No evidence for such a process was found in the full NA64 dataset of 2.84×10^{11} electrons on target. We place new bounds on the S, P, V, A coupling strengths to electrons, and set constraints on their contributions to the electron anomalous magnetic moment a_{e}, |Δa_{X}|≲10^{-15}-10^{-13} for the X mass region 1 MeV≲m_{X}≲1 GeV. These results are an order of magnitude more sensitive compared to the current accuracy on a_{e} from the electron g-2 experiments and recent high-precision determination of the fine structure constant.

Hunting down the X17 boson at the CERN SPS.

Recently, the ATOMKI experiment has reported new evidence for the excess of e + e - events with a mass ∼ 17 MeV in the nuclear transitions of 4 He, that they previously observed in measurements with 8 Be. These observations could be explained by the existence of a new vector X 17 boson. So far, the search for the decay X 17 → e + e - with the NA64 experiment at the CERN SPS gave negative results. Here, we present a new technique that could be implemented in NA64 aiming to improve the sensitivity and to cover the remaining X 17 parameter space. If a signal-like event is detected, an unambiguous observation is achieved by reconstructing the invariant mass of the X 17 decay with the proposed method. To reach this goal an optimization of the X 17 production target, as well as an efficient and accurate reconstruction of two close decay tracks, is required. A dedicated analysis of the available experimental data making use of the trackers information is presented. This method provides independent confirmation of the NA64 published results [1], validating the tracking procedure. The detailed Monte Carlo study of the proposed setup and the background estimate show that the goal of the proposed search is feasible.

Search for Axionlike and Scalar Particles with the NA64 Experiment.

We carried out a model-independent search for light scalar (s) and pseudoscalar axionlike (a) particles that couple to two photons by using the high-energy CERN SPS H4 electron beam. The new particles, if they exist, could be produced through the Primakoff effect in interactions of hard bremsstrahlung photons generated by 100 GeV electrons in the NA64 active dump with virtual photons provided by the nuclei of the dump. The a(s) would penetrate the downstream HCAL module, serving as a shield, and would be observed either through their a(s)→γγ decay in the rest of the HCAL detector, or as events with a large missing energy if the a(s) decays downstream of the HCAL. This method allows for the probing of the a(s) parameter space, including those from generic axion models, inaccessible to previous experiments. No evidence of such processes has been found from the analysis of the data corresponding to 2.84×10^{11} electrons on target, allowing us to set new limits on the a(s)γγ-coupling strength for a(s) masses below 55 MeV.

[EXPERIENCE OF BIPORTAL ENDOSCOPIC DECOMPRESSION IN LUMBAR SPINAL STENOSIS].

The aim of the study was to analyze the results of treatment with biportal endoscopic decompression of patients with spinal stenosis. The treatment results of 62 patients who underwent surgery (for discectomy) (for decompression) in the period from March 2018 to June 2019 were analyzed. All 62 patients were operated by biportal endoscopy at the spine surgery clinic of the State Institution "Institute of Traumatology and Orthopedics of the National Academy of Medical Sciences of Ukraine". Pain intensity was assessed using a visual analogue pain scale (VAS), patient satisfaction and quality of life was assessed using a modified MacNab scale and the Oswestry Disability Index (ODI), respectively, 1 week, 3 months and 6 months after surgery. Perioperative data were also evaluated (duration of surgery and length of stay in the hospital, blood loss and complications). X-ray results were evaluated using pre- and postoperative MRI (6-8 weeks after surgery). According to the results of studies in the postoperative period, a positive trend was observed. So, the indicator of back pain according to VAS after surgery decreased to 0,9±1,4 points, and the indicator of pain in the leg according to VAS on average in the postoperative phase was 1,28±1,1 points, respectively. Assessing perioperative data, in the group of patients the level of blood loss was 34,8±16,2, and the length of stay in the hospital was 2,9±1,3 days. Among the complications, 4 cases of point wound of the dural membrane and 1 case of linear wound of the dural membrane, more than 1 cm long with the contents of the dural sac entering the epidural space, which required conversion to an open operation with suturing the defect, were noted. Biportal endoscopic spinal surgery is an effective method of treating lumbar spinal stenosis, which has several advantages over open surgery (less tissue trauma, less blood loss, high patient satisfaction with the treatment result). UBE has an advantage over microscopic technique in terms of achieving complete decompression in an enlarged arthroscopic field without restricting the movement of the instrument due to the use of an independent portal, and continuous irrigation with saline during surgery is a great advantage to prevent infection.

[OUR EXPERIENCE WITH THE USE OF BIPORTAL ENDOSCOPIC SURGERY IN THE TREATMENT OF HERNIATED DISCS OF THE LUMBAR SPINE].

Open microdiscectomy is the standard surgical treatment for herniated discs at the lumbar level. However, with open operations on the spine, the risk of developing postoperative instability of the spine and the occurrence of chronic back pain is quite high. Biportal endoscopic spinal surgery is a new method in minimally invasive spinal surgery, which has several advantages over open surgery. The aim of the study was to analyze the results of treatment of patients with hernias of the intervertebral discs who underwent biportal endoscopic discectomy and compare them with the results of treatment with open microdiscectomy. The analysis of the results of treatment of 155 patients who underwent a diskectomy operation from March 2019 to October 2019 was performed: 67 patients were operated by biportal endoscopy in the spine surgery clinic of the Institute of Traumatology and Orthopedics of the National Academy of Medical Sciences of Ukraine, while 88 - The first patient was operated on by open microdiscectomy in the Ivano-Frankivsk Regional Clinical Hospital. Pain intensity was assessed using a visual analogue pain scale (VAS), patient satisfaction and quality of life were assessed using a modified MacNab scale and the Oswestry Disability Index (ODI), respectively, 1 week, 3 months and 6 months after surgery. Perioperative data were also evaluated (duration of surgery and length of stay in the hospital, blood loss and complications). X-ray results were evaluated using pre- and postoperative MRI (6-8 weeks after surgery). One week after surgery, the level of VAS back pain in the biportaldiskectomy group showed more significant improvements than in the group after open microdiscectomy. However, the comparative results after a 3-month and 6-month period for VAS (back and leg), ODI questionnaires, a modified MacNab scale, did not significantly differ between the two groups. In the biportaldiskectomy group, the level of blood loss (32.82±15.9) was lower, and the length of hospital stay (2.8±1.6) was shorter than in the group of patients after open microdisectomy (141.1±56.5) and (6.6±1.3), respectively. However, the duration of the operation (71.3±21.9) was longer in the biportal discectomy group than in the group after open microdisectomy (62.2±14.6), the difference was statistically significant. Biportal endoscopic spinal surgery is an effective method for the treatment of hernias of the intervertebral intervertebral discs of the lumbar region, which has several advantages over open surgery, namely: less tissue trauma, less blood loss, faster back pain regression after surgery, higher patient satisfaction with the result of treatment, and reduced hospital stay.

[EXPERIENCE WITH ENDOSCOPIC TRANSFORAMINAL MICRODISKECTOMY IN THE TREATMENT OF HERNIAS OF INTERVERTEBRAL DISCS OF THE LUMBAR SPINE].

The aim of the study is to evaluate the effectiveness of transforaminal endoscopic microdiscectomy in patients with herniated intervertebral discs at the L3 - S1 level of the lumbar spine. A retrospective analysis of the treatment of 468 patients with hernias of intervertebral discs of the lumbar spine was conducted, of them: 262 patients were treated in the Rivne Regional Clinical Hospital; 206 patients in the spinal surgery department of the State Institution "Institute of Traumatology and Orthopedics of the National Academy Medical Sciences of Ukraine". The study was conducted in the period from April 2016 to January 2019. In the preoperative period, all patients underwent an MRI or CT scan - examination of the lumbar spine, functional radiographs, and general clinical examinations were performed. According to the results of studies in the postoperative period, a significant improvement in the quality of life of the operated patients was revealed in accordance with the Oswestry Disability Index (the average for the group was 35,9%, which corresponds to a good result). There was a positive dynamics of pain in VAS (in the preoperative period - 8,8 ± 0,7 points; 6 months after the operation - 1,2 ± 0,5 points, with a predominance of lumbodynia and with an almost complete absence of radicular syndrome). In 28 (6,0%) patients, a hernia recurred within 6 months, however, in the remaining 440 (94,1%) patients, positive results of neurological symptoms were observed in dynamics. The obtained results confirm the high efficiency of ETD and the low risk of postoperative complications.

Dark Matter Search in Missing Energy Events with NA64.

A search for sub-GeV dark matter production mediated by a new vector boson A^{'}, called a dark photon, is performed by the NA64 experiment in missing energy events from 100 GeV electron interactions in an active beam dump at the CERN SPS. From the analysis of the data collected in the years 2016, 2017, and 2018 with 2.84×10^{11} electrons on target no evidence of such a process has been found. The most stringent constraints on the A^{'} mixing strength with photons and the parameter space for the scalar and fermionic dark matter in the mass range ≲0.2 GeV are derived, thus demonstrating the power of the active beam dump approach for the dark matter search.

FEATURES OF THE USE OF PHYSICAL EXERCISES IN THE REHABILITATION OF PATIENTS UNDERGOING THE PROCEDURE OF RADIOFREQUENCY NEUROABLATION OF THE HIP JOINT.

Among the various methods of treating coxalgia, the minimally invasive method of radiofrequency denervation of the sensitive nerves of the hip joint is becoming increasingly popular. Since the RFA technique is gradually beginning to be actively used in the practice of pain treatment, there is an urgent need for further rehabilitation of such patients in order to prolong the positive effect of the RFA procedure. The aim of the study was to develop a program of physiotherapeutic exercises for patients with coxarthrosis of the 3-4 stage, who underwent the RFA procedure of articular branches of the obturator and femoral nerves. The developed author's program was tested on 36 patients (37 joints) with coxarthrosis of 3-4 stages, who underwent outpatient treatment during 2017-2018. in the rehabilitation department of the State Institution "Institute of Traumatology and Orthopedics of the National Academy of Medical Sciences of Ukraine". The dynamics of the treatment results were evaluated after 2 weeks, 1, 3, 6 and 12 months after the procedure. Quantitative and qualitative assessment of pain was carried out on the basis of VAS pain. Joint functional limitations were measured using a Harris Hip Score (HHS). The use of physiotherapeutic exercises in patients who underwent RFA procedure n. femoralis and n. obturatorius positively affects the functional capabilities of the joints, which is confirmed by the results of studies on the Harris Hip SCOR and VAS questionnaire at all stages of observation. The use of physiotherapeutic exercises in combination with the RFA procedure of the femoral and obturator nerves in coxarthrosis can lead to a decrease in pain and stiffness, easier movements and increased flexibility, as well as maintaining the effectiveness of the RFA procedure for a longer period.

Search for a Hypothetical 16.7 MeV Gauge Boson and Dark Photons in the NA64 Experiment at CERN.

We report the first results on a direct search for a new 16.7 MeV boson (X) which could explain the anomalous excess of e^{+}e^{-} pairs observed in the excited ^{8}Be^{*} nucleus decays. Because of its coupling to electrons, the X could be produced in the bremsstrahlung reaction e^{-}Z→e^{-}ZX by a 100 GeV e^{-} beam incident on an active target in the NA64 experiment at the CERN Super Proton Synchrotron and observed through the subsequent decay into a e^{+}e^{-} pair. With 5.4×10^{10} electrons on target, no evidence for such decays was found, allowing us to set first limits on the X-e^{-} coupling in the range 1.3×10^{-4}≲ε_{e}≲4.2×10^{-4} excluding part of the allowed parameter space. We also set new bounds on the mixing strength of photons with dark photons (A^{'}) from nonobservation of the decay A^{'}→e^{+}e^{-} of the bremsstrahlung A^{'} with a mass ≲23 MeV.

Search for Invisible Decays of Sub-GeV Dark Photons in Missing-Energy Events at the CERN SPS.

We report on a direct search for sub-GeV dark photons (A^{'}), which might be produced in the reaction e^{-}Z→e^{-}ZA^{'} via kinetic mixing with photons by 100 GeV electrons incident on an active target in the NA64 experiment at the CERN SPS. The dark photons would decay invisibly into dark matter particles resulting in events with large missing energy. No evidence for such decays was found with 2.75×10^{9} electrons on target. We set new limits on the γ-A^{'} mixing strength and exclude the invisible A^{'} with a mass ≲100 MeV as an explanation of the muon g_{µ}-2 anomaly.

[Photons and protons in radiation therapy. The prospects for developing a proton therapy based on a new Russian accelerator]. / Fotony i protony v radiatsionnoi terapii. Perspektivy razvitiia protonnoi terapii na baze novogo otechestvennogo uskoritelia.

Body distribution of absorbed energy of ionizing radiation determines relations between the desired effect and associated radiation lesions. Common methods of photon radiotherapy are characterized by strong irradiation of healthy tissues. Accelerated protons enables an increase in gradient of doses between the radiation-exposed subject and adjacent tissues. It is thought valid to promote wider use of the new Russian proton accelerator for upgrading radiotherapy.

[The neurological syndromes in Lyme disease in children]. / Nevrologicheskie sindromy pri bolezni Laima u detei.

Clinical characteristics of Lyme disease (LD) course in children have been studied. Altogether 86 patients were examined. Serodiagnosis was made in patients basing on indirect immunofluorescence and enzyme immunoassay with LD agent antigens. Erythema--free forms, combination of mite-borne Borrelia infection with tick-borne encephalitis were detected. Two clinicoimmunological LD variants were verified: seropositive and seronegative mite-borne Borrelia infection with typical clinical manifestations. The disease took a benign course responsive to antibiotics in combined treatment of neuromuscular lesions.

[The peripheral neuromotor apparatus of patients with tick-borne neuroborreliosis (Lyme disease)]. / Perifericheskii neiromotornyi apparat u bol'nykh kleshchevym neiroborreliozom (bolezn'iu Laima).

Electroneuromyography and electromyography were performed in 48 and 102 patients, respectively, with Lyme disease-induced algic and amyotrophic syndromes. Electromyographic and clinical findings in the regions of the tick suction correlated. Multiple lesions of the nervous system may be considered as meningoencephalomyeloradiculoneuropathy as well as subclinical multiple mononeuropathy. Pronounced changes in the nerve potential against minimal shifts in peripheral nervous conduction reflect infectious-toxic nature of the condition.